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:
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.
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.
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:
- 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.
- 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.
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.