REI Flash 55 Backpack Review

REI Flash 55 Backpack Review

The REI Flash 55 Backpack is an ultralight, roll-top backpack with an optional top lid pocket. Weighing 2 lbs 10 oz, it has a mesh back to help keep your shirt dry in warm weather and numerous pockets and straps, called “packmods”, that can be removed or reconfigured to lighten it further, up to 7 oz. REI also added two additional side pockets to this year’s model, in addition to two side water bottle sleeves, in order to provide more external storage.  Make no mistake, the REI 55 is a true ultralight backpack and represents an exciting leap forward by the Co-op to make lighter weight backpacking more accessible and affordable. Plus, at $199, the price is right.  A Women’s REI Flash 55 Backpack is also available.

Specs at a Glance

  • Volume: 55L
  • Gender: Unisex and Women’s available
  • Frame: Internal, Perimeter Wire
  • Ventilated: Yes
  • Pockets: 10, including the main compartment
  • Total weight: 2 lbs 10 oz
  • Stripped Weight: 2 lbs 3 oz
  • Torso Sizing: (S: 18 inches), (M: 19 inches), (L: 20 inches)
  • Hip belt Sizing: (S: 30-40 inches), (M: 32-42 inches), (L: 34-46 inches)
  • Maximum recommended load: 30 lbs
  • Materials: 100-denier ripstop nylon main body; 420-denier nylon bottom; steel frame.

Backpack Storage and Organization

The REI Flash 55 is an ultralight-style roll-top backpack with an optional top lid. The advantage of using a roll-top is that it lets you compress loads from the top in addition to the sides using compression straps. This is useful if your load expands and shrinks during a trip, like when you resupply your food in town on a thru-hike or section hike. The nice thing about having an optional top lid is that you can add it when it’s needed, in cooler weather, for example, to carry extra gloves, navigation gear, or smaller items that are handy to have easily accessible on longer hikes.

The top lid pocket is handy in cold weather for gloves and hat storage
The top lid pocket is handy in cold weather for gloves and hat storage

The Flash 55 top lid is also a floating lid, which is important because the pack has a long extension collar that extends above the top of the frame. Having a floating lid lets you raise its height, so it sits properly on top of your load. It also lets you wedge gear between the top of the main compartment and the bottom of the top lid, like a bear canister, tent, sleeping pad, etc, without having to put it into the main compartment. That greatly expands the pack’s utility on more remote or technical trips.

The main compartment of the Flash 55 is huge and it will hold a lot of gear and food. It has a hydration pocket inside with a central hang loop, but the rest of the space is unstructured and the only access is from the top. REI also, in what may be a first, recommends lining the inside of the Flash 55 with a “trash compactor bag as a waterproof liner for your main compartment.” Needless to say, a rain cover is not included with the pack.

The Flash 55 has a front stretch mesh pocket which is large enough to hold a pair of crocks and a rain jacket
The Flash 55 has a front stretch mesh pocket that is large enough to hold a pair of crocks and a rain jacket

The Flash 55 has a mesh front pocket that makes it easy to store damp or frequently accessed items, so you don’t have to stop and open up your pack to access them or put them away. The top of that pocket also hooks onto a plastic dongle for added security. One concern I do have is on the durability of the mesh used on the front pocket and the side water bottle sleeves discussed below. While the mesh holes are small to prevent snagging, I question its durability for long-term use and off-trail. Solid fabric pockets or pockets made with stiffer, heavier duty mesh are much more durable.

REI Flash 55 Backpack


Ultralight and Ventilated

The REI Flash 55 is a highly configurable, ventilated, roll top backpack that weighs 2 lbs 10 oz, but can be stripped down to 2 lbs 3 oz by removing several optional components. If you've never owned a backpack that's this lightweight, the Flash 55 is a good ultralight pack to cut your teeth on.

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The Flash 55 has two mesh water bottle sleeves (located directly behind the hip belt pockets but attached to the pack sides) to make it easy to reach the bottles while you’re wearing the pack. The bottles sleeves are sized for tall skinny soda or bottled water bottles and it’s easy to pull them out or replace them while wearing the pack. While you can also fit a 1 liter Nalgene in the mesh sleeve and pull it out, getting it back in is difficult because the bottle diameter is wider. Both bottle sizes also have a tendency to pop out of the sleeves when you put the pack down or its falls over. The sleeves have snap closures in front to hold the bottles in place, but they’re not totally effective, and they’re difficult to re-snap closed when wearing the pack.

REI has also added to solid paneled side pockets behind the water bottle sleeves for holding gear and longer objects, like tent poles, chair kits, fishing poles, etc, and lashing them to the side of the pack with a compression strap. It’s an important enhancement, especially on a pack that will be used for long-distance trips. These pockets are not reachable when wearing the pack.

The Flash 55 has side pockets for gear storage and mesh sleeves to hold water bottles
The Flash 55 has side pockets for gear storage and mesh sleeves to hold water bottles

There are four additional pockets on the Flash 55, all of which are optional and can be removed. The floating top lid has an external top “Rainshield” pocket. That pocket is made with two layers of fabric and seam-taped, making it highly water-resistant. I hesitate to call it waterproof because internal condensation is bound to make anything inside damp in prolonged rain. The top lid is attached by buckles and can be easily removed, as well as the straps holding it to the pack.

The hip belt pockets are sized to hold a SmartPhone
The hip belt pockets are sized to hold a SmartPhone.

The hip belt pockets are also easily removable. One is mesh-faced and the other has a solid fabric front. They’re large enough to hold an iPhone 6, a small point and shoot camera, or snack bars, but aren’t what I’d call big. They’re held on with a clever webbing strap/toggle system that holds them in place and prevents them from flopping as you bounce down the trail.

Simple webbing and plastic dongle attachment system
Simple webbing and plastic dongle attachment system

The Flash 55 also comes with a Rainshield shoulder strap pocket that’s attached to the shoulder pads using the same webbing/toggle system used by the pockets. It’s sized narrow for a Smartphone or a small camera. It snaps shut with a magnet, which always makes me leery on a backpack because it can interfere with a magnetic compass…but it’d be easy enough to cut out and replace with a velcro patch. It’s constructed like the top lid, with two layers of fabric and seam-taped, making it highly water-resistant. This pocket is a real value-add and saves you the expense of buying a similar accessory pocket.

The Flash 55 includes a shoulder pocket sized for a SmartPhone or small camera.
The Flash 55 includes a shoulder pocket large enough for a SmartPhone or small camera.

Backpack Compression and External Attachment System

The stock REI Flash 55 comes with an elaborate but easy-to-use compression and external attachment system. You can use it out the box, as-is, remove the numerous straps (without having to cut them off), or move them around anyway you need.

All the packs straps are attached to the cord daisy chains so they can moved or removed.
All the pack straps are attached to the cord daisy chains so they can be moved or removed.

The four vertical corners of the pack have daisy chains loops running down them, implemented using cord, instead of traditional webbing. This is an increasingly common feature found on trail running backpacks, but it hasn’t really caught on yet with mainstream backpacks.

All of the straps and attachment points on the pack are girth hitched to the daisy chain instead of being sewn into the pack seams. This lets you detach them, move them to a different location, or change their angles, as needed.

REI even includes a mesh sack with the Flash 55 so you can store the straps you’ve removed between uses, and not lose them. Directions for attaching the straps are printed on the outside. Thoughtful.

The Packmod strap attachment directions are printed on the outside of the storage sack
The Packmod strap attachment directions are printed on the outside of the storage sack

All of the removable straps and pockets weigh 7 oz total. If you’re trying to reduce your pack weight, the biggest bang for the buck comes in removing the pockets (listed below), not the straps.

  • the top lid w/ Rainshield pocket (1.9 oz)
  • two hip belt pockets (1.6 oz)
  • Rainshield shoulder strap pocket (0. 6 oz)
  • two, two-piece upper side compression straps w/ buckle
  • two, one piece lower side compression straps
  • trekking pole/ice axe shaft holder
  • two rear, short straps for top lid w/buckle
  • two front, long straps for top lid w/buckle

The problem with removing the side compression straps is that you often can’t anticipate when you’ll need them to lash gear to the side of the pack. If you remove the top lid, you can get rid of up to four straps, though I’d still recommend keeping two of them to hold down the sides of the roll top. There are a lot of variations possible, though.

The Flash 55 roll top can be closed at the top or along the sides
The Flash 55 roll-top can be buckled closed at the top or along the sides. Doing it along the sides prevents vegetation from getting caught in the pack, especially off-trail.

Backpack Frame and Suspension

The REI Flash 55 is a ventilated backpack with a suspended mesh panel to help keep you cooler and your shirt drier in warm weather. The mesh is stretched across soft dorsal and lumbar padding and integrated with the pre-curved wings of the hip belt. This provides a comfortable back-hugging fit, but won’t pull you backward and off-balance, because the ventilation cavity is not as deep as that found on comparable packs, like the Osprey Exos.

The Flash 55 has a ventilated back to help keep your shirt drier
The Flash 55 has a ventilated back to help keep your shirt drier.

The Flash 55’s frame is a lightweight, 360 degree steel perimeter wire (not removable). It provides great torsional flex, so it moves with you, as well as the horizontal rigidity that is important for proper load lifter function and hip belt load transfer. The hip belt is sewn directly to the pack so that the load is carried very close to your core muscles and hip girdle for maximum efficiency, while the soft lumbar pad and pre-curved hip belt wings grip the iliac crest. I’m really quite impressed with the hip carry on the Flash 55, which is comfortable and does not slip down.

The hip belt closes with pull-forward straps for mechanical advantage, with a single central buckle. The hip belt pockets are positioned a little farther back on the hip belt than I’d like, so I can’t see the zippers when I look down my sides, but whether they are for you will depend on your physical dimensions. I think the hip belt sizing for both the men’s medium and large sizes is optimistic in the upper half of the sizing range, but your mileage will vary. However, if the front of the hip belt doesn’t cover your hip bones, the pack isn’t going to fit you (See How Should a Backpack Hip Belt Fit?).

If you remove the top lid, consider keeping two of the top lid straps to anchor the sides of the roll top
If you remove the top lid, consider keeping two of the top lid straps to anchor the sides of the roll top.

The shoulder straps have a unisex S-shape, with a rail-based sternum strap. They’re thickly padded and covered with a breathable mesh to wick away sweat. Both shoulder straps have elastic hose keepers as well as a pair of short horizontal webbing straps to attach the Rainshield shoulder accessory pocket, which can be easily moved to the other shoulder strap.

The sizing ranges for the men’s Flash 55 pack are quite narrow in terms of torso lengths and hip belt sizes (see specs above), so I’d encourage you to try on a few different sizes to zero in on a comfortable fit. Based on the numbers, I should be able to use a Flash 55 in a medium, but the large size fits better, both in the torso and the hips. If you’re between sizes, I’d definitely recommend sizing up.

Comparable Backpacks

Make / ModelWeight (oz)Ventilated
REI Flash 5542Yes
Granite Gear Crown 3 - 60L36.7No
Hyperlite Mountain Gear SW 340032.11No
Osprey Exos 5843Yes
Gregory Optic 5843.35Yes
Zpacks Arc Blast 5521Yes
Mountain Laurel Designs Exodus 5718No
Mountainsmith Scream 5545No
Sierra Designs Flex Capacitor41.2No


The REI Flash 55 is a highly configurable, ventilated, roll-top backpack that weighs 2 lbs 10 oz but can be stripped down to 2 lbs 3 oz by removing several optional components. If you’ve never owned a backpack that’s this lightweight, the Flash 55 is a good ultralight pack to cut your teeth on. Fully configured and out-of-the-box, with its top lid and full compression system, you can use it as your existing backpack as long as you don’t exceed its maximum recommended load of 30 lbs or gear, water, and food weight. If you want to experiment with removing the lid and just using the roll-top, or in removing components, you can do that when you’re ready. Regardless, I think you’ll still be impressed at how well the Flash 55 carries compared to a heavier-weight backpack with a more substantial frame.

If you’re a more experienced lightweight backpacker, switching to the Flash 55 can provide you with a lower-cost way to reduce your pack weight than other comparable packs, with more features, and more flexibility. It’s also a far better backpack in my opinion than an Osprey Exos 58 (see our review) if you prefer a roll top. That’s saying something because this pack is the industry leader for a sub 3 pound, ventilated backpack at the $200 price point. My advice would be to try out the REI Flash 55 and compare them for yourself. This pack is a winner.

Disclosure: The author purchased this backpack.

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  1. I’ve hiked 2+ thrus and have used a lot of low weight gear. I’m at the technical definition of UL, but have often needed to carry up to 30 lbs with food and water. Also, I have a somewhat-warranted distaste for REI (another story, I’ll spare you…). And yet, though I have not used this pack, just considering the design, the assessment here seems spot on. Bring your gear to REI, put it in there, and try it on. If it fits you and your gear, go for it.

    It’s esp nice that it will let you continue to drop weight/features you don’t need, as you become more experienced.

    One note of caution… ventilation tends to be overrated as a spec. I tend to prefer designs similar to the one here, where it doesn’t make any false promises about keeping your back from sweating. It just helps your shirt dry faster in the evening, when it cools off, IF you are still moving. If you make camp at 4pm, and that’s before your body has stopped sweating, it won’t gain you much. (And the other ventilated designs won’t either.) So, while I offer my meager endorsement to this design, I caution low expectations for reduced back sweat.

    • Ventilation is overhyped. If you carried 30 pounds on your head (perfect ventilation) your back will still sweat.

      • I agree – when you’re hiking hard, you’ll sweat. Does ventilation help – I suppose, but (like Gore-Tex) it’s a case of “better than what we once had,” not a miracle cure. I hike frequently in 90-degree, 90% humidity conditions. I sweat. (I also sweat when it’s cold.)

        The best-ventilated packs today are no better than the external-frame packs I used when I started hiking around 1980, and there’s a perfectly good reason: the new stuff (including Osprey’s Levity, Exos, and Atmos series) are the same basic design as those Camp Trails and Kelty packs of long ago. They’ve been updated with higher-tech materials (just like tents and clothing), but they still use the basic design: a perimeter frame and a trampoline back panel. That’s why all of them still tent to move the load away from your back, and why we feel some “bounce” to the pack. Today’s designs aren’t as far away as the “classics,” so the tendency to pull against you as you turn is pretty much gone, but other than that, it’s the same pack. (The pack bags have gotten significantly better, though.)

        If you want body-hugging, you’ll need to look at internal-frame packs; they are intended to hug your back (sweating is accepted, here) and keep the load close to the center of gravity. If you want to see a good comparison of internal and external, take a hard look at the design elements of the Osprey Exos versus the Osprey Kestrel.

  2. You mention you prefer it to the other similar price & weight ventilated, what do you think of it compared to the Crown 2 and Flex Capacitor?

    • I like the Granite Gear Crown 2 because it has an adjustable length hip belt and none of the fixed length hip belt sizing issues of the Flash 55. I also like the pockets / compression system / external attachment options on granite gear packs a whole lot – plus it has much bigger hip belt pockets. The crown 2 38 has actually turned into one of my favorite packs.

      The Flex capacitor is a good pack, but not a roll top. I’ll really like roll tops. Still its a far more durable pack than the Flash 55. Its a good pack if you beat your packs to death.

      Different people have different needs and preferences for different trips and regions. Half the battle is figuring out what you need a pack to do. Picking one is pretty easy after that.

      • I really liked the Granite Gear packs I’ve owned (original Vapor Trail, a Nimbus, a couple of Vargas, and a crown VC.) They were great: the lightest, most comfortable pack I ever carried and very well built. They are internal frame, and very well-balanced.

        The only reason I no longer use them is a Goldilocks story: the small ones are too small, and the large ones are too large. The largest load I carry now just fills a 45-50 liter pack nicely; the small GG packs are in the 35-40 liter range, and the larger packs are in the 55-60+ liter range. If they come out with a 45-50 liter range, I’ll definitely be giving them s good, hard look.

      • I have the Granite Gear x Massdrop Crown X60, just curious how this stacks up

      • “Half the battle is figuring out what you need a pack to do. Picking one is pretty easy after that.” Could almost frame that.

  3. Unfortunately I have a 19 inch torso and a 30 inch waist. Probably would not work for me.

    • You’ll be at the very end of the adjustment of the waist straps in a Medium, but the shoulder straps would be good probably, it would be close. I’m similar measurements

  4. These REI UL backpacks are well made and a good deal for the money. I’ve owned the 1st two models with the Cruise UL 60 being the last. That was when I first got into UL backpacking. They served me well.

    But when I tried an Osprey EXOS 58 I immediately sold my well-used Cruise UL 60 and got the EXOS. More comfortable overall, especially the cooler mesh trampoline back support.

  5. Hi Philip,
    Are those additional side pockets large enough to fit a thermorest z lite foam pad?

  6. Hi Philip, this pack has a lot of foam (back panel, etc.). Does the foam used absorb water?

    • The foam itself doesn’t but some will “stick” in the holes that pass through it by surface tension. All packs absorb some water, even DCF ones, in the shoulder straps and hip belts which are covered by fabric. If it rains, ah-hem, you’re going to get wet from internal condensation even if you’re wearing rain gear. I wouldn’t worry about it too much.

  7. I’ve read a ton of reviews on different packs lately, and this is the best review I’ve ever read, by a country mile.

  8. I stopped at the REI in Ann arbor Michigan. They had a good supply of women’s and men’s. Despite my 30 inch waist the size small and medium both seem to fit well.

    I loaded both the flash and the osprey Exos with 23 lb. For me the flash was much more comfortable. I noticed on the Exos that the shoulder straps we’re very narrow really cut in and almost wanted to twist.

    The frame on the flash is more flexible than the exos but still rather stiff. the one thing I noticed with the flash is that when I walked around it seemed to shift a little more side to side but not a lot.

    • Hey, Nate, I’m the same dimensions as you. I tried this pack on at REI today and liked it. Please update if you bought the Flash, which size you went with, and how it performed for you (with how much weight) in the field. Thanks.

  9. Probably won’t be getting until June. Will update for sure.

  10. I’m torn between the REI Flash 55 and Osprey Levity 60 – any thoughts?

  11. This was super helpful, thank you.

    I’m planning a 6 day trip through europe over the summer and am looking for something versatile and light. The only comments I’ve heard against it are that it doesn’t have as many compartments as the osprey so access to specific material is slightly more challenging. But this, I think is something that can be circumvented with a little bit of strategy. I also don’t like the idea of the osprey weighing me down with pockets I will hardly use.

    Do you feel comfortable strapping gear to the outside of the pack? Such as sleeping bag, etc.

  12. I went into REI today armed with my 20% coupon expecting to leave with the Flash 55. Unfortunately, neither the medium or large would fit me properly. I bought a Flash 45 in 2017 and I love it. The best pack I have ever owned. But, I would like something a bit larger for some extended trips I have planned. My 2017 version of the Flash 45 was completely adjustable, but, as Philip noted, the new version of the Flash 55 is not adjustable. I’m bummed out. That’s progress I guess. The 2017 version of the Flash 45 has a floating lid so I am hoping I am going to be able to jam everything I need in there.

  13. For tall-torso guys like me:

    One modification I made to the Flash 65, and it may work for the 55 as well:

    6 long strips of velcro, attached back to back, so you get one side fuzzy, and one side prickly. Un-stick the back panel that attached the straps to the pack, and “extend” the velcro attachment panel with the strips, so that the pack sits lower.

    Made a world of difference for me.

    • Hey Phillip, I just read this review and am considering this bag. I don’t live anywhere close to an REI or I’d go try one on… I’ve got a 19.5″ torso and 32/34″ waist. Do you have a size recommendation based on your experience?

  14. Will a Therm-a-Rest NeoAir XTherm Sleeping Pad fit in those extra pockets on belt??? And by the way awesome review. I think I might pull the trigger with anniversary sale coming up.

  15. I just picked one up today and, I must say, I am very impressed with what REI has done here. They have stepped up their game big time, because this pack is legit! I’m going backpacking this weekend thru next Wednesday, in The Gila. I like bringing my fly rod with me on trips like this and there is plenty of room for my backpacking fly setup.

    One knock I will say about it so far is that it does not fit my BV500, horizontally. I have the Small size. I’m curious if the Medium or Large will fit it this way. I’ve always packed with it like that, so I’ll have to switch things up when hard-sided food canisters are required.

  16. It doesn’t show up in your review, but I’m interested in a comparison between the Flash 55 and the ULA CDT, which is a frameless pack. I’m trying to find a good lightweight pack for my girlfriend, who is new to backpacking. I myself have a ULA Ohm 2.0, and I really like that brand. Big differences I see between the CDT and the Flash 55 is a frame and back ventilation (which other commenters point out as being overrated). I plan on carrying all the heavy stuff, so I think a frameless backpack would be ok for her.

    • The CDT is basically just a sack because it has no frame. It requires more advanced skills and experience to pack. Do you girlfriend a favor and buy her something with a frame for her first backpack, even if it’s just a polyethylene board. You can always cut it out. If you think she’s only going to go on trips with you, you’re fooling yourself.

  17. Thanks for the great review. Any convenient way to store a Zlite on the exterior of the pack? I can’t tell if the straps are long enough, or if any of the pockets are big enough…

  18. Great review! My wife purchased one earlier this year and has used it on a few trips in Yosemite and Canada and has really liked it. I’ve tried it on in the store and also worn my wife’s a bit and I too found it more comfortable than the Exos.

    I’d like to hear your thoughts on the Flash vs the gossamer gear silverback 55. Namely comfort-wise and if the silverback is worth the extra $$. Both seem very similar in design and weight and are currently my two front runners for my next pack.

  19. Being a bit overwhelmed with backpack options, at the moment I’m considering the GG Mariposa, the ULA Circuit and the REI Flash 55. What are your thoughts about these options? Any preferences? is always my first stop when looking for well thought out reviews. Thanks!

    • Need more context to be honest. They’re all fine packs. Where do you plan to use them? What’s important to you? Why can’t you decide between them?

      • I plan to use the pack in the Mid-Atantic and New England, spring, summer and fall. I’m looking for a light pack that can handle up to 30 lbs relatively comfortably. My usual base weight is 15-16 depending on the temps. Important features are a roll top and a stretchy pocket in front(?) for easy access to stuff and to stuff a wet tent fly. I prefer simple with few or at least removable extras. Does this help?

        Why can’t I decide? I suppose because they all seem good. And now a friend has recommended the Osprey Exos 58 which also looks good. I guess I’m indecisive.

        • I’d get the ULA circuit. It has a rolltop (the mariposa and exos don’t) and is less fussy than the REI.
          They are all good packs. For good or ill, we are drowning in good backpacks but they all have their nuances.
          The exos doesn’t have hip belt pockets. Acceptable pack, but the huge ventilation arch makes packing awkward.

  20. Thanks Philip. I’ve been leaning in that direction but there are so many choices to consider.

  21. I’m a tiny woman attempting to buy my first serious backpack… and I’m super divided between the REI Co-op Flash 55 and the Granite Gear Crown2 60. They’re both within my price range, ultra light and carry about the same volume.

  22. I bought this pack this year. After several trips into the woods with it, I can attest to its performance and durability. It is a great pack! I love the water bottle pockets – I can reach them with ease even with my 1.5 liter nalgenes. And, it holds all my gear to a several-day backpacking trip. I am a larger hiker, and this pack fits me well. I would definitely recommend it for anyone looking to go lighter weight.

  23. I purchased this pack as a replacement for my Osprey Atmos – WHAT a difference this pack has made. Sure it shaved a bit of weight, but the comfort of this pack compared to the Osprey is what makes it particularly amazing!! I’ve taken it on a number of trips so far, and will find myself forgetting that I’m carrying a pack at all! Even on a recent trip to the ADK’s when I had to add a bear canister and my pack weight was approaching 30 lbs, I didn’t experience any discomfort.

    Another benefit I’ve found is that it feels far more attached to your body then does the Osprey with the suspension – and I don’t notice any real difference in the sweat factor between this and the Osprey.

    Highly recommended!

  24. Hi,

    I was looking at the Flash 55 and noticed that the hydration hose exit ports near the shoulder straps seem like easy entry points for rain / precipitation. Was this something you noticed / was concerned about?
    Have you noticed any leaking into the main compartment through those hose ports? Any tips to prevent that from happening?

  25. Ughh. I agree lots of good choices for backpacks but they each have their nuances. I put 3,000 miles on my Osprey Aura 50, mostly 5-600 mile European hikes not carrying a tent or stove. I loved it! I want to go lighter. I am a 62 year old female, 5’4″, 132 lbs; and between a comfort and ultra light hiker. I am planning on doing the PCT in 3-4 sections. I went into REI and was very frustrated having to choose between the Osprey EJA 58 and the REI Flash 55. I am getting overwhelmed with all the reviews, but I felt yours are the most thorough. What is your suggestion? Thanks, Moira

  26. While this pack is not in my market search, mostly due to lack of hip and shoulder adjustments, I did notice one potentially fatal flaw in the design. The water bottles being located so far forward and into the user’s lower ribs puts them into a location that can result in rib/chest injury on small slips and falls. If side-hilling a steep slope, it’s not hard to slip a little and bang the side/bottom of the pack into the mountain. Not a serious scenario in itself in most cases, but with a hard/full water bottle, especially a smartwater bottle, it will potentially jab right into the rib cage with a very serious amount of force.

    I had a Gregory Baltoro with the flip-out water bottle holder that points the bottle right into the rib cage. This literal exact thing happened to me while carrying a water bottle in the holder during a scramble over some slick moss and rock. Falls in this area are a given and usually result in no more than a bruised ego. In my case, it came darn close to cracking a rib. Carrying a heavy pack with a messed up rib, let alone a cracked one, is diabolical levels of agony.

    It makes me wonder if this safety aspect is something that other pack designers take into account? It seems very logical to put the heavy water bottles as far forward as possible for balance and ease of access, so I can’t imagine REI somehow figured out something no other pack designers thought through.

    The REI Flash in actual use by many people is very unlikely to result in massive injuries, but the safety factor is something to consider for people who like to travel deep and solo on off-trail pursuits.

    I solved the issue of normal packs being difficult to access the side water bottles when wearing the pack… by just growing longer arms. I highly recommend growing longer arms. :)

    • Big Agnes doesn’t make silnylon tents. I don’t believe they ever have.

      • I think mine is a poly silicone nylon blend of some sort? Whatever it is, it’s very slippery material. It’s the Copper Spur UL1, which has been out of production for quite a while? I think I read it has nylon fabric with one coating of silicone on one side and polyurethane on the other for seam sealing?

        If you know what was used in this tent model, I would curious to know as well. You’ve clearly used way more tents than I have. :)

  27. I am thinking to use this pack to hike the JMT next year in August/September. I’m looking for a light pack that can handle up to 30 lbs relatively comfortably, including a bear canister. My usual base weight is around 16.
    I already have a Mountain Laurel Exodus and I was wondering if it makes sense to get this pack. I tend to sweat a lot and the Flash looks more breathable. Do you have any recommandations. Thanks,

    • it’s not that much more breathable. I’d get yourself a proper suspended mesh pack if that’s what you want. The Osprey Exos 58 or the forthcoming Gregory Focal 58 that is due out in the new year.

  28. Great balanced review. I bought a Flash 55 for myself and a Zulu 65 for my son late last summer. I spent way too many hours trying to find a bag that was lightweight and vented but still had fairly substantial support and padding, not an easy task. Apparently there aren’t that many of those packs around. I also really wanted multiple side pockets which is also very rare. The Flash and Mariposa were the main two. Tried on the Exos. Felt like the padding was too thin and lack of pockets was a deal breaker. Osprey is a great company though. Wish they updated that pack a bit. Also tried the Blaze 60. It’s light with a substantial frame, more so than the Crown2. The Flash just fits like a glove on me and the Blaze was not quiet my fit, great bag though. Blaze feels 3x more durable than the Flash. That’s about my only gripe with the Flash, it would benefit from a bit more durable main fabric and less mesh. The padding on the Flash is stellar. The pack really hugs my back and feels like an extension of me vs the Ospreys which feel like they “hang off you”. Gregory just came out with the Focal 58 which appears to be one of those magical middle of the road packs, light with good support. Same weight as the Flash. Not sure if the materials are more durable or if the padding is comparable. Nice suspended frame like the Exos with the upgrades many of us want. I’d love to see your review of it!

  29. Been using this pack for a couple years. My context is often multi-day backpacking for wilderness trail building & maintenance. Phil’s review is generally spot on. I’ve bought and used more packs than I care to mention, and after extensive use I must say nothing touches this pack for it’s combination of price, weight, durability, comfort, capacity, and modularity. The reinforced bottom, side pockets, tilted bottle holders, and daisy chain + pack mod are the killer features for me. With the right pack mod straps placement, this thing compresses down to daypack size really well. I never use the lid.

    The only flaw in my eyes are the pockets; they are all too small for my smartphone, so I leave them behind. I have a Gossamer Gear shoulder pocket that I like to use on the hip belt for my phone, which works really well. Also agree with Phil about the long-term durability concerns with the mesh front pocket, but I mitigate this with strapping my Litesmith sit pad on the front to protect and provide easy access. Zero holes after a couple years, and I take this pack on/off 50+ times a day and set it on the front during trail building. The mesh on the bottle pockets is still a concern, but holding strong for me. Bottles popping out can be an issue, but mostly with tall/narrow/slick bottle like smart water. Using wider Gatorade or Powerade bottles that have the ridges helps with that. But I’ll gladly deal with this to have access to water with my poor shoulder flexibility.

    We all have different requirements no doubt, and REI stuff is not in with the UL cool kids and their arbitrary “any pack over 2lbs is blasphemy!”, so this pack is often overlooked. But for the rest of us, this is a killer pack. Given REIs unmatched return policy, there is nothing to lose if you are on the fence….try it!

  30. Great review. What would be your preference between the Zulu 55 and the REI Flash 55?

  31. Hi! I just bought a Flash 55 for an upcoming trip and I’m wondering where to put my sleeping pad? I use a Nemo Switchback. I scoured the internet and called REI and no one seems to have any idea other than using a different kind of sleeping pad. Thoughts? TIA!

    • What’s wrong with scrunching it under the floating top lid, under the side compression straps, or attaching elastic cord to the front of the pack and sliding it over the front mesh pocket?

      • I thought one of the side pockets would be the spot but it doesn’t fit. There are loops on one side of the bottom. It would have been so easy for them to put two more loops for lash points on the bottom of the pack, like my Osprey Tempest 40. I’ll put it under the brain. Thanks!

        • I went back to REI today and there is a place to put the straps under the bag. It is a little hard to find and not intuitive but the extremely knowledgeable salesperson showed me how to set it up.

  32. “trash compactor bag as a waterproof liner for your main compartment.”

    This might be a first for REI, but it’s the most common recommendation for “waterproofing” portage packs for canoe trips.

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