REI Flash 55 Review

I tested the REI Flash 55 backpack and this is my verdict.

April 05, 2024
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This pack is perfect for a backpacker who wants a full-featured pack at an ultralight weight, a “Goldilocks” of backpacks. The REI Flash 55 is an accessible backpack that offers thoughtfully placed pockets, durability, and recent upgrades at a competitive price. It has a heavier weight than most ultralight packs, a limited size range, and just two color options.

Product Overview

REI Co-op Flash 55

Price: $199

rei co-op flash 55

✅ Inexpensive

✅ In stock and immediately available

✅ Comfortable

✅ Plenty of pockets for organization

✅ Semi-customizable “Packmod” system


❌ Fragile outer pocket on older styles

❌ Not waterproof

❌ Limited sizing

❌ Limited capacity

❌ Heavier than most ultralight packs


  • Weight: 42 oz. | 2 lbs. 10 oz. (Womens XS)
  • Weight/Load Capacity: 30 lbs
  • Volume/Carrying Capacity: 55L
  • Fabric: Nylon Robic (100D & 210D)
  • Frame Material: Steel
  • Frame: Full-perimeter frame with additional mid-back reinforcement
  • Frame Type: Internal Frame
  • Suspension System: 3D contoured hip belt, padded shoulder straps, load lifters, sternum strap, foam back panel
  • Number of Exterior Pockets: 9 + main compartment
  • Hipbelt Pockets: Yes

The REI Flash 55 is an ultralight backpacking pack with a 55-liter volume capacity and a 30-pound weight capacity. At 42 oz., the Flash is at the upper limit of ultralight packs. At its most basic, with all removable accessories stripped, it weighs 35 oz. The 3D contoured hipbelt and padded back create a comfortable and sturdy feel.

With 9 external pockets and 1 internal pocket, it boasts more than any other ultralight pack. It is extremely water resistant, though a pack liner is still suggested. The REI Flash 55 is a good fit for hikers who need a lightweight, durable pack with has strippable features for a variety of loads and is very comfortable.

Unlike many made-to-order ultralight packs that may have lead times of weeks to months, this can be ordered and full of your gear in just days. Because it is available in REI stores, the Flash 55 is ideal for someone new to long-distance backpacking and would like to be professionally fitted and try their pack on before purchasing.

Though the weight of the REI Flash 55 scares the most ultralight, I argue that its strengths are worth the weight. The comfort, affordability, durability, and convenience that this pack provides are worth the extra ounces.

For other ultralight backpack reviews, read our post on the best ultralight backpacks.

Performance Test Results

rei co-op flash 55 performance score graph

How We Tested:

I have used the Flash 55 for over 2500 miles through all conditions: freezing temperatures, an extremely rainy summer, and hot summer days. I thru-hiked the Appalachian Trail, did a long section hike on the Appalachian Trail, and have made multiple weekend trips in the Midwest with this pack. It has even seen the odd plane trip in the four years that I have owned it.

Weight: 7/10

The REI Flash 55 is considered an ultralight pack because it falls under the 3-pound threshold. With all the pieces attached, it weighs 42 ounces, but his pack is also moderately strippable. If you remove the hipbelt pockets, shoulder pocket, brain, and daisy chain attachments, it will save you a total of 7 ounces.

In its completely stripped-down mode, this 35-ounce pack will still offer five external and one internal pocket. This is possible because of its 100- and 210-denier Robic nylon construction, durable but very light materials.

Though it boasts a ton of features for its weight, this pack is relatively heavy compared to other ultralight packs. There are definitely more lightweight, simple ultralight packs out there, but the majority of backpacking packs with this many pockets and attachments weigh significantly more than the REI Flash 55.

a hiker with rei flash 55 backpack

Price: 9/10

At $199, the REI Flash 55 is a great price for a high-quality product. In fact, it is one of the cheapest full-frame packs that fall under that 3 lb. ultralight threshold. You may be able to snag one even cheaper if you strategically use one of the often-available REI coupons.

The Flash 55 is one of the most versatile, durable packs and offers one of the most comfortable carries, making it a great overall value. Factor in the REI warranty and the value is even greater. The value of trying on the pack before purchase cannot be underestimated here. A REI employee will measure your torso, fit you to the correct size (even if your torso length and hip size are different), adjust the straps to an accurate fit, and weigh the pack to simulate a full load.

Because it is sold online and in the many REI stores nationwide, the REI Flash 55 is readily available. REI offers free 5-7 day shipping and free store pick-up. If you need it immediately, you can get the Flash 55 shipped in as little as one day.

front and back rei flash 55 backpack
Retailing at $199, Flash 55 is one of the most versatile, durable packs on the market.

Storage and Capacity: 9/10


I could give the Flash 55 a 10/10 in this category– with one exception. The one imperfection of the Flash 55 in this category is the advertised capacity compared to the actual capacity. REI advertises a 30-pound load limit, though I have comfortably carried more weight in the Flash 55 in a pinch. The large, main storage area fits a large amount of gear while the multitude of front, side, hipbelt, and shoulder pockets make organization easy.

The back pocket on older versions of the Flash 55 was a mesh pocket with a toggle and loop closure– a very weak material held closed by an unreliable closure. On new versions, though, these problems have been fixed! Newer versions of the Flash 55 include a nylon back pocket with a buckle closure.

I used a women's XS size, which has an actual capacity of 53L with all of its pockets. Because I choose to hike without the large brain top pocket, the actual capacity of my pack in use is just 50L. This, in my opinion, is plenty of space for most ultralight gear loads, though I have not tried to fit a bear canister in it. With a roll-top closure, the pack easily adapts to smaller loads.

hiker carrying rei flash 55


On both sides of the back pocket are two deep side pockets, made of nylon with elastic at the opening. Outside of these pockets are two removable compression straps, which help to hold the contents of the pockets securely. I use one to keep my foam sit pad handy and the other to house large items like tent stakes.

The two water bottle pockets are angled forward and are located between the deep side pockets and the hipbelt pockets, making them easy to reach without taking your pack off. These mesh hydration pockets, one on each side, even have one snap that allows the opening of the pocket to be narrowed, keeping thin bottles from sliding out.

The removable shoulder pocket is the perfect size for a cell phone, Garmin device, or even a wallet. It is made of nylon, with an envelope-style magnetic opening. Because it is not stretchy, larger cell phones would not fit in it. I chose to remove this pocket and replace it with a larger third-party shoulder pocket that boasted improved water resistance, two pockets, and zipper closure.

rei flash 55 hipbelt side view

Hipbelt and Interior

The two removable hipbelt pockets are each .5L capacity. One is made of stretchy mesh, the other made of waterproof nylon, both with zipper closures. I chose to use the mesh pocket for snacks, while the nylon pocket stored my bug lotion, sunscreen, blister balm, and chapstick.

The removable upper brain boasts a 3L capacity, made of waterproof nylon with a zipper closure. In newer versions, this converts to a waist pack when removed. The interior of the backpack has a large pocket for a water reservoir. When not in use, this pocket lays flat against the frame and does not take up space.

rei flash 55 hipbelt
I would have used a smaller hipbelt if it was an option.

Comfort: 10/10

The REI Flash 55 is known for its comfort. It has a very comfortable 3D molded hipbelt and back panel, frame, padded mesh shoulder straps, removable chest straps, and load lifters. Even at its maximum capacity, the weight is comfortable.

The hipbelt and back panel are molded in a way that creates a seamless feel, with no uncomfortable joints. Both are padded with a dense foam, but covered with a breathable mesh. That comfortable mesh extends onto the adjustable shoulder straps. Even on the hottest days of summer, the Flash 55 was comfortable and I only experienced one day of shoulder strap chaffing.

The Flash 55 includes many adjustment points, allowing a customized fit. In older models, the compression straps, shoulder straps, waist belts, and load lifters all adjust to distribute weight comfortably and evenly. Newer models have added the ability to extend the torso length, allowing packs to accommodate those who are still growing or enabling the ability to share packs between people of different heights.

using rei flash 55 backpack1
The exterior pockets add crucial capacity.

Features: 10/10

The Flash 55 is as fully-featured as ultralight packs come and have nearly every feature a long-distance hiker could need – exterior back pocket, water bottle pocket, removable mesh hipbelt pocket, compression straps, daisy chain attachment loops, adjustable torso and more. Some ultralight hikers may argue that the Flash 55 has more features than necessary, but many are removable to customize individual luxury levels.

Adjustability: 8/10

The Flash 55 is very adjustable, both in sizing and adaptability, though it falls short on some adaptations that other backpacks offer. As a new feature of the recently released version, hikers can adjust the torso length of the pack. As previously noted, this allows the pack to grow with hikers who may get taller and allows the bag to be shared between hikers of different heights.

This joins the list of adjustable features including hipbelt length, chest strap, load lifters, compression straps, total capacity, and attachments, which REI calls “packmod” features. A few things on the Flash 55 are permanent though. The frame and back panel cannot be removed.

Due to its molded construction, the hipbelt cannot be removed or replaced with a different size hipbelt. By the end of my thru-hike, I would have benefitted from replacing my hipbelt with a smaller size, as I have done with my Gregory pack.

rei flash 55 whistle

The whistle is built into the chest strap for convenience in an emergency.

As a solution, REI does offer mixed sizing bags, like a women's XS pack with an M waist belt. Though this meets an existing sizing need, it is not a permanent solution for those whose weight and size may fluctuate. This lack of sizing inclusion is reflected in the stocked sizes of the Flash 55. Available women's sizes: XS, S, XS torso/M hipbelt, and M. Available men's sizes: S, M, L torso/S hipbelt, L.

Waterproofing/Resistance: 6/10

The REI Flash 55 is moderately water resistant. While the fabric that comprises the majority of the backpack is water resistant, in practice, the contents of the pack will get wet. With a body made of ripstop nylon, the pack only absorbs water in its mesh areas and does not become significantly heavier in the rain. Because the pack has sewn, untaped seams, some water works its way inside the pack.

I was interested to find that the majority of the moisture actually comes in– and out– of the bottom panel of the pack. The bottom panel is made of a semi-porous fabric. In theory, this is good because any moisture that finds its way inside the pack will be released through the bottom of the pack, not held inside.

On a long, rainy day, however, you will end with a backpack that is dripping from its bottom onto your shorts. The simple and inexpensive solution is to use a waterproof pack liner, which keeps my pack contents perfectly dry inside my damp pack.

using my rei flash 55 backpack
The multiple loops can be used creatively based on your gear needs.

Durability: 10/10

REI’s Flash 55 is extremely durable. My pack has been with me for 6 years and nearly 3000 miles, in every season, and has many trips left in it. Though the nylon has a few snags on the exterior from rocks and general wear, there are no holes. The main weak point of my pack, the mesh back pocket seen on older styles, has been replaced by a sturdier fabric pocket in new versions. For an ultralight pack, the Flash 55 is surprisingly durable.

rei flash 55 interior

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About Kelsey "Lizard" Gerig

Kelsey "Lizard" Gerig is a nature educator, summer camp director, and backpacker. Coming from an "indoorsy" family, Kelsey dove head first into the world of backpacking, beginning with a 400-mile trip and completing a thru-hike of the Appalachian Trail just three years later.

About Greenbelly

After thru-hiking the Appalachian Trail, Chris Cage created Greenbelly to provide fast, filling and balanced meals to backpackers. Chris also wrote How to Hike the Appalachian Trail.

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