REASONS TO BUY
Main compartment gobbles up gear
Durable fabric
Comfortable back and hip padding
REASONS TO AVOID
Limited sizing and no torso adjustment
More expensive than better performing packs
REI Co-op Flash Air 50 Review
A well-designed pack that takes inspiration from cottage brand trends and reimagines them for the mainstream
The REI Co-op Flash Air 50 is familiar, but much lighter than the conventional backpacking backpack you're likely used to.
Credit: Justin Simoni
By Justin Simoni ⋅ Review Editor ⋅ June 10, 2026
RELATED: The Best Ultralight Backpack of 2026
Our Verdict
The REI Co-op Flash Air 50 starts with a fairly conventional backpack design and goes to work removing unnecessary weight, ultimately arriving at an ultralight pack. It has the bones of a conventional backpacking backpack, with padded shoulder straps, back, and hip belt, all melded onto a body made of thin, light UHMWPE ripstop nylon. Taken together, it offers much of the comfort of a backpack that weighs many pounds more, while also appearing to be as Spartan as the lightest-weight backpacks from cottage brands. If you're just starting to lighten up the base weight of your backpacking kit, this pack could be a good place to start.
Compare to Similar Products
 This Product
REI Co-op Flash Air 50 | |||||
|---|---|---|---|---|---|
| Awards |  Best Overall Ultralight Backpack |  Best Bang For Your Buck | |||
| Price | $299 List Check Price at REI | $315 List | $279 List | $275 List | $92 List Check Amazon (on sale!) |
Overall Score  |
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| Star Rating | |||||
| Bottom Line | A well-designed pack that takes inspiration from cottage brand trends and reimagines them for the mainstream | This pack wowed us with its perfect set of features, comfortable design, and impressively large carrying capacity | A tough, voluminous, and reasonably priced ultralight backpack that's perfectly designed for long trips | You can carry silverback-sized loads with supreme comfort, thanks to this pack's excellent design, which transfers pack weight from your shoulders to your hips | A compelling option if other ultralight packs are simply too expensive |
| Rating Categories | REI Co-op Flash Air 50 | Gossamer Gear Maripo... | Durston Kakwa 55 | Gossamer Gear Gorill... | 3F UL Gear Qidian Pro |
| Comfort (40%) | |||||
| Ease of Use (25%) | |||||
| Weight-to-Volume Ratio (20%) | |||||
| Adjustability (15%) | |||||
| Specifications | REI Co-op Flash Air 50 | Gossamer Gear Maripo... | Durston Kakwa 55 | Gossamer Gear Gorill... | 3F UL Gear Qidian Pro |
| Measured Weight | 32.0 oz | 34.3 oz | 31.0 oz | 32 oz | 31.0 oz |
| Stripped Weight | 27.0 oz | 18.0 oz | 27.5 oz | 16.2 oz | 31.0 oz |
| Advertised Volume | 50 L | 60 L | 70 L | 50 L | 56 L |
| Measured Volume (Main Compartment) | 45 L | 54 L | 55 L | 45 L | 53 L |
| Weight per Liter (Full Pack) | 0.64 oz/L | 0.57 oz/L | 0.44 oz/L | 0.64 oz/L | 0.55 oz/L |
| Sizes Available | Torso: S, M, L | Torso: S, M, L Hip Belt: S/M Curved (w/ S torso), M Straight (w/ M and L torso); other hip belts sold separately |
Torso: S, M, L Hip Belt S/M, M/L |
Torso: S, M, L Hip Belt: S/M Curved (w/ S torso), M Straight (w/ M and L torso); other hip belts sold separately |
Torso: One size |
| Organization Compartments | Side pockets, center pocket, dual zippered pockets on hip belt, shoulder strap phone pocket, main compartment | Top flat zippered pocket, three total side pockets, center pocket, dual zippered pockets on hip belt, main compartment | Side pockets, side zipper pocket, center pocket, hip belt pockets, strap pockets, main compartment | Top flat zippered pocket, side pockets, center pocket, dual zippered pockets on hip belt, main compartment | Side pockets, center pocket, hip belt pockets, main compartment |
| Hydration Compatible | Yes | Yes | No | Yes | No |
| Side Pocket 700ml Smartwater Capacity | 3 | 3 | 3 | 3 | 2 |
| Single Hip Belt Pocket Capacity | 5 Clif Bars | 6 Clif Bars | 10 Cliff Bars | 6 Clif Bars | 10 Cliff Bars |
| Removable Frame and Hip Belt | No | Yes | No | Yes | No |
| Sternum Strap Whistle | Yes | Yes | No | Yes | No |
| BearVault BV500 Compatibility | Good | Good | Excellent | OK | Good |
| Frame Type | Spring steel shaped frame, non=removable foam padded back | Removable SitLight foam pad / removable stay | Removable foam pad / removable stay | Removable SitLight foam pad / removable stay | None |
| Fabric | UHMWPE ripstop nylon (87% nylon/13% polyethylene; bluesign approved) | 100D & 210D recycled Robic nylon | Challenge Ultra 200x | 70D & 100D recycled Robic nylon | UHMWPE mixed nylon |
Our Analysis and Test Results
Weighing only 32 ounces, the REI Co-op Flash Air 50 rightfully earns its place in our ultralight backpack review. The plush back padding and supportive hip belt really set this pack apart from other packs we tested, some of which shave weight by removing padding altogether.
The Flash Air 50 is lightweight and supportive, making it a comfortable carry through rocky terrain. Credit: Justin Simoni
Likes
The Flash Air 50 doesn't compromise on comfort. It has a fully integrated, shaped hip belt that efficiently transfers the pack's load to your hips. Fully integrated back padding also provides good airflow, which is a nice break from other ultralight packs.
No matter how haphazardly you packed this backpack before dawn, a removable internal metal frame helps keep the pack rigid and comfortable. Load lifters up top round things out, offering a lot of adjustment of how the load rests on the top of your back.
The foam back panel allows plenty of airflow onto our back, hips, and shoulders. Credit: Sam Schild
The hip belt has a center snap, with dual adjustment buckles, one found on each side. Credit: Justin Simoni
Load lifters have long straps to easily grab and provide a lot of adjustment. Credit: Justin Simoni
If you're familiar with the company's more conventional backpacks or daypacks, you'll probably feel right at home with the Flash Air.
Small features abound. One of our favorites is the divided side pockets – the back segment is more secure, and the front is designed to be more easily accessible without having to take off the pack. We're also happy to see a useful top “Y” strap that makes it easier to carry a bear canister.
Each side of the REI Co-op Flash Air 50 actually has two pockets, with the smaller one designed to be reach easily to grab items like water bottles while you're on the go. Credit: Justin Simoni
A bear canister can be securely attached to the top of the pack using the top “Y” strap. Credit: Justin Simoni
Dislikes
This pack still has one leg firmly in the conventional backpack world. Even though it's trying to be as light as possible, it's partly missing the point of why someone might choose a lighter-than-normal pack.
Although the total weight is reasonable, it isn't outstanding. The Flash Air 50 weighs 32 ounces, but we measured a rather meager 45 liters of internal capacity. The manufacturer's listed load limit of only 20 lbs also seems quite low, especially considering the internal frame. Similar packs are advertised with a load limit more than twice that of the Flash Air 50.
With the integrated back padding and hip belt, there isn't too much that can be removed from the main pack body, except the internal metal frame, and the optional pocket and ditty bag. Credit: Justin Simoni
We applaud a larger manufacturer throwing their hat into the ultralight ring, but the Flash Air 50 may benefit from another revision. There's a removable shoulder strap pocket, but it's not the right shape to fit a water bottle or flask. This pack has a reservoir port to feed a tube through, but lacks a pocket to house the reservoir internally. An additional mesh ditty bag is included, but we couldn't figure out how to attach it to the pack, and we're not exactly clear on its purpose.
And although the hip belt and back padding are nice to have, it would be even nicer if they were removable options. Not only would this allow you to really dial in the fit, but if the trip allowed, you could easily strip them off to drop the base weight.
The small front side pocket is angle to easily grab things on the go, but we sometimes found it hard to put items back. Credit: Justin Simoni
Should You Buy the REI Co-op Flash Air 50?
While larger manufacturers can often deliver a great product at a competitive price, cottage-industry brands have produced better packs that cost about the same, or in some cases, even less than the Flash Air 50. If past performance is any indication, the next revision of this pack will be better than the one we tested.
What Other Ultralight Backpacks Should You Consider?
The Gossamer Gear Gorilla 50 is an even more comfortable backpack, with a stout internal frame that locks into a supportive hip belt. While it's more minimalist than the Flash Air 50, we liked it better, and it's cheaper. For folks switching from a conventional backpack, the Osprey Exos Pro 55 is another option with a familiar form that's more comfortable and more adjustable than the Flash Air 50.
—Justin Simoni
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