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REI Flash 50 Backpack

REI Flash 50 Backpack

The REI Flash 50 backpack is the smallest multi-day pack in REI’s line of ultralight backpacks. With a base weight of 2 lbs 10 oz, it is possible to remove some of the features of this pack to further reduce it’s weight to 1 lb 13 oz.

That’s sounded like a breakthrough of sorts and I decided that it would be interesting to understand the features it offers, how it carries with different gear selections, and some of the design decisions that went into making the Flash 50 so lightweight.

Here’s a brief video that provides an overview of the REI Flash 50:

Key Features

Large central compartment – the bulk of the pack’s 50 litre (3050 cubic inches) capacity is in a large central pocket that closes with a drawstring closure.

Shovel pocket – this is a signature feature in many REI packs and is useful for storing wet gear, coats, or a climbing helmet. It is located on the back of the central compartment and does not have a top lid, allowing fast access to its contents without having to open the central compartment.

Floating lid – this pocket has two compartments, a zippered pocket on the top of the pack which is useful for storing hats, gloves, and snacks, and an internal pocket on the bottom of the lid that faces the top of the central compartment. This internal pocket is good for storing flat documents such as maps. The floating lid can be removed from the pack saving 3.8 oz in weight.

Hydration capable – there is an hydration sleeve on the inside of the central compartment for holding a hydration reservoir. There are plastic hooks at the top of the back of the pocket for suspending a reservoir, hydration ports on the right and left side of the central compartment, and elastic loops on the shoulder straps for securing a hydration hose.

Removable frame sheet with adjustable stays: It is possible to bend the frame sheet stays to tailor the pack for your needs, but you can also remove the frame sheet and the stays saving an additional 9 oz in pack weight.

Side mesh pockets – the pack has side mesh pockets sized to fit one liter bottles.Unfortunately, it is not possible to reach back and grab a bottle while you are wearing the backpack.

External attachment points – the Flash 50 has external attachment points on top of the floating lid, at the bottom of the main compartment and on the outside of the shovel pocket allowing you to hang sleeping pads, bags, or extra food containers on the outside of the pack.

REI Flash 50 Frame Sheet

Removable Frame Sheet and Adjustable Stays

Gear and Backpack Compatibility

When selecting a backpack, it’s handy to bring all of your gear to the store so you can see how it carries and whether your gear is compatible with the design of the backpack. Don’t assume that your gear will work with any backpack. You may have to repack it or change your packing system to get it into a new pack.

Backpacking Gear

A Load Testing Methodology

REI recommends the Flash 50 for 2-5 days trips with 25-40 lbs of gear. Given those specs, I decided to test the pack by loading it up with several different combinations of gear and food to see if there were any constraints on the type of gear that can be carried in the pack and how the pack would feel.

First, I defined a base load that weighs 11 lbs and is representative of what I carry in my backpack on colder Autumn trips, including:

Base load

  • Western Mountaineering Ultralight 20 sleeping bag in stuff sack
  • Therm-a-rest NeoAir Sleeping Pad
  • Heavy long underwear for sleeping, wool socks and 1 pair extra socks in a stuff sack
  • Montbell Thermawrap camp jacket and Waldies camp shoes
  • First aid and gear repair kit, maps, and toilet paper bag
  • Canister Stove, pot, large fuel canister, and Ursack kevlar bear bag
  • Rab Momentum eVent Shell, Golite Reed Rain Pants, hats and gloves
  • Spot GPS Messenger, Cell Phone, Digital recorder, Brunton Compass, BD headlamp, BD mini lantern

To this, I added some variable components that I added to the bag in different combinations. The variable components add approximately 10-14 additional pounds to the test weight, bringing the total contents to about 21-25 lbs.

Variable Components

  • 2 L Platypus water reservoirs, filled or 2 x 1 Liter water bottles, filled
  • 2 day food bag (3.2 lbs) or 4 day food bag (7.4 lbs)
  • Black Diamond First Light Tent (short length in stuff sack) or a Scarp 1 Tarptent (long length in stuff sack)

Load Testing Results

Max Weight Configuration, 2 lbs 10 oz, with Floating Lid and Frame Sheet

First off, the Flash 50 doesn’t work well with tent like the Scarp 1, which packs up in a long roll. To pack it, you need to stand it up in the main compartment of the pack (which is problematic if it is wet), attach it to the outside of the pack below the central compartment or above the floating lid. Neither of these last two locations is optimal from a load distribution standpoint because the heavy tent is not close to your center of gravity, where you want your heaviest gear to be packed.

Instead, the Flash 50 works well with tents that pack up in a short stuff sack, separate from their poles – and this is how you’d have to repack the Scarp 1 if you wanted to use it. This makes it possible to pack the tent in the shovel pocket if it is wet to segregate it from the rest of your gear, while making it easy to pull out and dry when you stop for a break.

Next, packing the Flash 50 with the base load, 4 days of food, a 2 L hydration reservoir (filled) and the short Black Diamond tent is a very tight fit, although achievable. However, the side mesh pockets become unusable because they are stretched tight against the body of the pack. Removing the hydration bladder does not alleviate the tension on the side mesh pockets.

When worn with a full hydration reservoir, the pack feels like it’s strongly pulling away from your shoulders. This feeling goes away when the hydration reservoir is removed.

Reducing the food load from 4 days to 2 days does not alleviate the tension on the side pockets, which I found surprising, but it gave me an important clue about one of the weaknesses in the Flash 50 pack design.

From bottom to top, when I pack the central compartment of a backpack, I put my sleeping bag on the bottom, then my food bag, tent, extra clothes, and then my inflatable sleeping pad. The reason I do it this way is to locate the heaviest weight, which is in my food bag and tent, as close to my hips and the small of my back as possible, so it is close to my center of gravity.

However, packing your food bag higher up in the central compartment of the Flash 50, relieves the side pressure on the mesh pockets enough, that they become usable again. You lose efficiency of movement because of this, which I consider undesirable, since your shoulders are taking up more of the load and not your hips.

Padded Back Panel of REI Flash 50

Min Weight Configuration, 1 lb 13 oz, without Floating Lid and Frame Sheet

For completeness, I continued my testing of the Flash 50 without the frame sheet to see what else I could learn about the pack. I was surprised by the results!

I started out by pulling out the frame sheet and packing the base load with 2 days of food, 2 x 1 liter water bottles, and the small Black Diamond tent. When I put on the pack, it felt great!

I was astonished by this because I thought that the frame sheet was responsible for all of the Flash’s rigidity and that I’d need to add something along the lines of a z-lite or nightlight sleeping pad to the pack to hold it up. Instead, I discovered that the backing for the padding on the back panel on the pack provides it with all of the rigidity required. This was a pleasant discovery.

So I added in the hydration reservoir to see if it felt different without the frame sheet as well. Unfortunately, using a hydration system still pushes the center of gravity too far away from your core and it feels like someone is trying to pull you backwards.

So I took out the hydration system and increased the food load from 2 to 4 days. That turned out to also be surprisingly comfortable without the frame sheet, but the side mesh pocket became unusable again which is problematic since you need to use water bottles.


If you’ve braved through all that detail, you’ve probably learned more about me than about this pack.

If you’ve skipped to the end, here are my conclusions about the REI Flash 50.

Don’t use a hydration bladder with this pack. It totally throws the pack off balance and you’ll feel like the pack is pulling you backwards.

For 25 lb loads, you don’t need the frame sheet, and if you pack carefully, you can remove the floating lid. That’s huge, because you’re pack weight drops to 1lb 10 oz, which is true ultralight in my book.

If you plan on using water bottles, you’ll be limited to 2-3 days of food if you want to carry it close to your hips. You can probably stretch this to 4 days of food, but you might need to bag it into separate bags to distribute the volume and so that the side mesh pockets remain accessible.

Unless you bring a bowling ball or a gallon jug of whole milk with you when you go hiking, I don’t see how you can exceed 25 lbs of gear weight in the Flash 50. There’s simply not enough volume to hold it. That makes me question why there is even a frame sheet in this pack to begin with, but I guess REI needs it for marketing purposes. It’s probably easier for them to sell a pack that weighs well over 2 lbs, than one that hovers too close to the 2lb barrier.

Is the Flash 50 worth $149. Heck yes!  If you want to get a lightweight pack that helps you get under 3 lbs of pack weight, but you’re not ready to get an sub-pound ultralight backpack from a cottage manufacturer, I’d recommend you go with this pack. It will provide you with a lot of flexibility and room for experimenting with different gear and packing combinations. I owned the predecessor to this pack, which was my first truly lightweight pack, and put many miles on it.

Disclosure: The author owns this product and purchased it using their own funds.
Written 2010.

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  1. Great review! I've always been tempted to test out some of the REI packs. Most of their other gear(clothing) that I have tested are fantastic values! Keep it up!

  2. I was rather amazed to find that REI had a pack this lightweight available, but there also seems to be an industry trend amongst the more mainstream manufacturers to put add some sub-3 lb packs to their product lines. REI has always had a distinct backpack line and I think their packs stack up pretty well on the basis of value.

  3. What pack have you been using with the Scarp 1, and how would you compare it to the REI pack?

  4. Great review! I,m psyched to see you're doing videos. Looking forward to more reviews and show and tells. Ken H

  5. I've mainly used my Gossamer Gear Mariposa Plus with the Scarp 1. I've reviewed the MP+ here – it's a true UL pack and a much better mate to the Scarp 1 than the REI Flash 50. The side mesh pockets on the MP+ work when the pack is stuffed and the high mesh pocket is a perfect match for the long body of the Scarp 1. I think I explained that the Scarp is not a good match for the REI Flash 50 above, because of it's length. Other than that there are many many differences between the packs, suffice to say that heaviest configuration of the MP+ is lighter than the lightest configuration of the REI Flash 50, even though the MP+ has a significantly larger capacity and only costs $30 more.

    I've also used the Scarp 1 with a Cold Cold World Chaos, but that's a winter mountaineering pack and not something I use for 3 season backpacking.

    If you're interested, I'm posting a sale on used shelters on Friday and the Scarp 1 will be available for purchase. I'm switching to tarps 100%.

  6. More videos and pack reviews in the pipeline! Thanks for the encouragement.

  7. I own the women's version of the pack (the Flash 50 from 2009) and have to disagree with some of what you've wrote. I think a lot has to do with how you pack it. I carried 8 days worth of food and gear while using the pack backpacking in the 100 Mile Wilderness and up to Katahdin and thought it was very comfortable the entire way, and I had room to spare (I used a 3 liter hydration bladder). I start with the Six Moon Designs Lunar Solo tent (which does pack smaller than the Scarp) and ThermaRest Neo-Air 66" pad as my bottom layer, then put my Mt. Hardwear Phantom 32 sleeping bag inside my Evernew cookpot upright on the left side of the pack and my clothing and headlamp/repair sacks on the right side of the pack forming 2 columns on top of the tent/pad layer. My toiletries and bear rope get stuffed in open areas, and I split my food into 2 bags that go on top of the cookpot/clothing layer. Final top layer is my Caldera Cone stove/fuel bottle and collapsible Nalgene Canteen "dirty" water carrier. Total pack weight starting out with 8 days food and water was 34 lbs. I agree with you about the side mesh pockets not being large enough to carry water bottles when the pack is full, but I use them to carry snacks, bandannas and sunscreen/bug spray instead and am able to access the snacks while I hike and don't have to take off the pack. I use the front vertical zip pocket to carry my rain gear and rain cover, and the shovel pocket to carry my first aid and bathroom kits. I often leave the top lid pocket at home unless I'm on a long trip. But even then, I only use the lid for items such as my cell phone and eye glasses. Lastly, I attach my Crocs (camp shoes) to the outside using the elastic attachment cords that come with the pack. Otherwise, nothing else gets attached externally, so there aren't a lot of extra items dangling off the pack.

    I've also used this pack with my Bearikade 6-day bear canister inside, packed horizontally, on a 3-day backpack trip in the Adirondack High Peaks carrying food for 2 people. My feeling is that it actually is very well designed to make the most of it's volume and one doesn't need a pack that's larger.

    The pack is also an excellent winter day pack, because it has attachment points to strap on snowshoes, and removing the framesheet makes it a lightweight pack that has enough volume to handle all the extra gear for a winter day hike, yet will roll down to a very small size if you want to carry it inside your overnight pack.

    Of course, the thing about backpacks is that what works great for one person is not good at all for another, and that's why everyone should bring all their gear to try it out before buying a pack – great advice!

    • Thanks so much for your review debmonster!!! I am wanting to buy the 50L for myself but i was so worry it was going to be to small and wasn’t sure if i’d be better off with the 65L. Now that i’m reading your review i think the 50L will do me just perfectly :)
      Thanks so much again..

  8. I agree with you completely. It all depends on how you pack your gear and it's compressibility. That's why I tried all of these gear combinations. There's no way to tell how a pack will carry unless you spend a few hours packing and unpacking it.

    But I think we agree that the way you need to pack the Flash 50 is to put your larger items up higher in the main compartment, because the side mesh and the shovel pocket constrict it lower down. That how it sounds like you're packing it: that you're not using the hydration pocket, and you've located your food fairly high up, under your dirty water reservoir. My preference is to put heavier items closer to my hips and back, but I imagine the womens version of this pack is also somewhat different than the mens, so we may be comparing apples and oranges.

    I agree that this pack is the right size for most multi-day backpacking excursions, even something as extreme as the 100 mile wilderness as long as you keep you non-consumables weight down, which you obviously did. The Flash 65 is monstrous in comparison.

  9. Glad to see a review of the REI Flash 50 pack, Phil. As you know, I tested this pack across Scotland earlier this year on the 200 mile TGO Challenge. I used the framesheet, a Platypus hydration bladder and carried 3-4 days food after re-supply, and found the pack very stable – in fact a pleasure to carry.

    I have not used the Flash without the framesheet, other than for a day hike before venturing out overnight. I don't like the idea of adjusting the contents to substitute for a framesheet particularly in bad weather but maybe I'll take your advice and try the "no framesheet" option sometime.

    There are issues with using bladders as such (especially when residual water in the tube spills out in my tent!) but I didn't experience any with regard to stability with the Flash 50.

    As you note, the shovel pocket is very useful. This is where my wet TN Laser Competition went most days, on the outside of the pack, along with all sorts of other items – trowel, MSR wind shield, trash etc. The pocket is one with the mesh side pockets and is therefore large.

    With regard to the floating lid, personally I find this space provides useful storage. Removal will of course reduce capcity by a couple of litres, which may or may not be acceptable.

    The comment about the framesheet and REI marketing policy is perhaps a little too cynical. Do potential buyers really say 'this pack doesn't feel heavy enough to me'? In my view, REI, like most manufacturers, overestimate the space required for trips hence the "2-3 nights" tag. But perhaps this is no more than saying most packs are not marketed for lightweight backpacking. And some folk like to carry all sorts of trappings when they go into the back country even if only for a couple of nights.

    Overall, I'd highly recommend the Flash. And for the price it's a bargain. Hey, this is sounding too much like a puff now, but then I am a big fan of REI :-).

  10. I couldn't remember if you had the Flash 50 or the Flash 65. Yes, the 50 is a nice pack and I really like the way the hip belt feels on me. I can see now why you found it comfortable on the TGO.

    Sorry about the marketing cynicism. I have inside info from the UL manufacturers that people view packs under 2 lbs as less durable, so I could see why manufacturers would want to stay above the 2lb number.

  11. Great review! Very insightful. I do have a question about the sizing, what size torso do you have? I think this pack size L is rated for 17"-19". Would you agree with recommending it only to that size demographic?

    Personally I have a very difficult time finding a smaller pack to fit my 23" torso according to the listed specs, and have been reluctant to purchase a lighter pack because of this issue.

  12. I wear an 18" pack. The problem with sizing most mainstream commercial packs for me is that the torso lengths only come with hip straps in certain sizes, none of which reflect the fact that older people get a bit thicker around the hips with age.

    A 23" inch torso is large, but you'd be better off having a pack made custom by a cottage manufacturer to get the precise fit you need. Custom packs don't cost that much more than commercial ones.

    Good Luck. I have another regular (on the blog-roll) named Jolly Green Giant and he is also quite tall.

  13. A good lightweight pack that comes with the option to swap out the hipbelt is the Granite Gear Escape AC 60. Weighs 3 lbs. and my hiking partner used it for 8 days on the AT and said it carried 30 lbs. very comfortably.

  14. Same with the Gossamer Gear Mariposa Plus and the Gorilla. The hipbelt comes in three lengths, and rumor has it that Gossamer Gear will also be make longer torso sizes for tall people. Grant Sible, the head of the company, is also a tall guy.

  15. great review. I use the flash 65 which I think improves on the 50. First it is bigger and only weighs 9 oz more. It has 4 outside mesh pockets; one on each side and then the same shovel pocket extension like the 50. You still can't get bottles out of them (unless you are double jointed) but they do allow things to be carried on the sides with the shovel pocket full. I always use the framesheet as it transfers the load perfect for me. My base weight is 23 lbs and I carry a 2L bladder. I carry my Tarptent (rainshadow2) strapped to the bottom of the pack. My wife and I did a 104 section of the PCT this summer and the pack performed perfectly. I have used the this pack without the framesheet as a day pack but found the pack too big, so I bought a flash 18 for day hiking. I don't like the only one pocket on the hip belt and have added a clip-on pocket to the other side. I have looked at other packs, but unless you are willing to go frameless (which I am not yet) the 65 seems to weigh less or equal to the others and as you pointed out; it sure cost a lot less than the others.

  16. Dennis – I agree with everything you've said about the 65 – in fact I have a review of it coming out next week. It is much larger than the Flash 50 and the extra mesh pockets really help. It's a good value pack that's ideal for backpacking with a partner or for family backpacking.

  17. I am probably going to return my Flash 50 I don't like how you have to super compress your sleeping bag super small just to cram it in the bottom pack. I realize I could put the sleeping bag higher up in the pack but I don't feel I should need to do that. I will probably end up getting the MP+. Really that is my only qualm with this pack other than what everyone has been saying about the side pockets not holding water bottles easily. I do like that on the top compression strap their is a mini pocket which can fit a lighter, a key, etc. Another cool feature for the people like pockets is the the floating lid has a velcro pocket on the underside of the lid for even more space. I wish the hip belt had 2 pockets instead of just one. I like to stick micro trash I find on the trail in that pocket. I think I will ultimately have to make my own reusable trash bag that hangs on the side. I tend to find no less than 5 lbs of trash on every hike or backpacking trip I do.

  18. Had a chance to try one of these out last weekend in the Henry Coe state park in California (flew in a couple of days early for a scientific meeting). I'd bought this because it looked much more "airline proof" than the mairposa. It was pretty comfortable for a 28 mile (or so) weekend – though it did get a bit sore on the shoulders after a long day (17 miles). It does take some practice packing & I'd have a bit of trouble with more than 4 days food as you can't easily just strap on an extension bag like with the mariposa (might be possible, but I'd have to look carefully). It is fairly water resistant, but I'd recommend a pack cover to keep water out of that back pocket. Having the key clips was good for one of these in and out trips, because I just clipped my keys there and forgot about them. The upper pocket was also useful for things like a camera that you want to get quickly. In the airport, the back pocket just fits my laptop and it's easy to retrieve for scanning so it's a good travel pack.

  19. I have a Flash 50 and love it. I have loaded this pack with 30-35lbs of gear and trekked the Northern Presidentials in NH for 5 days with no issues.

    I have recently decided to work towards true UL (under 10 lb base) and started by removing the floating lid and internal frame for this pack. Although I was still not true UL as I was just under 13 lbs base, I was extremely comfortable. I had none of the above mentioned issues and my pack included (among other things) an uncompressed sleeping bag on the bottom, 2 liter camelback reservoir and 2-16oz soda bottles in the mesh side pockets. I never had an issue with the pack pulling away or reaching any of my water bottles.

    I may be replacing my bag but only to get something lighter (8 oz). My son is dying to get a hold of my Flash 50 MVP!

  20. Been looking at this pack since this summer when I realized my Osprey was just way too heavy for over nighters. Went to buy it recently and it is on sale but the large is gone for good. Just talked to REI and the new version will be coming out in February 2012. I will probably get it then, seems like a great starter pack and it would trim almost 3 pounds off my pack weight. Assuming the 2012 65L will be releasing at the same time as it is also on clearance.

    • I’m surprised they never released a 2012 50L Flash Pack. Ended up picking up the 2011 on clearance and I absolutely love it. After rereading your review, I’m going to try it out without the frame and without the lid as well. I think I paid around $60 for it.

      • Everything you say about the pack is true, but if you remove the lid and the framesheet you now have a heavy frameless pack that competes unfavorably with the Gossamer Gear, Six Moons Designs and ULA packs. The problem I have with the shovel pocket on the Flash packs is that it doesn’t expand very well and ends up taking space from the main pack area. The pack companies above use a mesh pocket that has a lot of expansion area. They also offer large pockets on the hip belt which I think are great.

      • I was excited because I thought it was a step in the right direction for REI. They’ve since pulled the product from the market and gone backwards in pack design/base weight.

        Weight-wise the frameless, lid-less version of the Flash 50 weighs pretty darn close to comparable, GG, Six Moons, and ULA packs. The back mesh pocket on those packs performs much better, as you note, but we can’t expect everyone who buys from REI to buy from those manufacturers. Which is why I review gear from other manufacturers like REI, to be honest.

        Good bargain Maz – you scored.

  21. I think the Flash 50 is a really good value. The 65 is a good pack too but it is enormous, maybe way more capacity than you need if you're already cutting gear weight and volume.

  22. Yep you got it, need to cut volume as 60L is way too much space for 3 season over-nights or even weekend trips so no use in carrying extra bag weight around.

    The more I hike and backpack, the lighter I want my gear to be, especially in the Whites. Thanks for the super thorough review and vid by the way.

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