REI Co-op Flash Air 50 Backpack Review

REI Co-op Flash Air 50 Backpack Review

REI’s First True Ultralight Backpack Weighs Less Than Two Pounds

We’re thrilled to see REI pumping out Co-op brand ultralight gear, and the sub-two-pound REI Co-op Flash Air 50 might just be their crown jewel. Shop now.

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  • Weight: 30 oz
  • Price: $299
  • Materials: UHMWPE ripstop nylon
  • Frame: Shaped spring steel piping
  • Load Capacity: 25 lbs (likely a conservative estimate)
  • Internal Volume: 40L
  • External Volume : 10L
  • Pros: Ultralight. Very comfy pre-curved foam hip belt & padded back panel. Fair value. Load lifters. Minimalist design.
  • Cons: Slim exterior pocket profiles decreases usable volume. Pad mod detachable pockets are lackluster. No daisy chain on shoulder straps. Top Y-strap too narrow. Bladder tube ports lets rain in.

Compare to more great option in our guide to the best backpacking backpack, or view a side by side deep dive of Flash 55 vs Flash Air 50.

back panel of REI Co-op Flash 50 backpack
profile view including water bottles in side pockets

Overview of Construction & Features

For starters, you can think of REI Co-op Flash Air 50 like a streamlined version of REI’s esteemed Flash 55 backpacking pack, including a very similar aerated foam back panel, pre-curved hip belt, and pocket configuration. Where it differs is the use of lighter weight fabrics, lack of torso-adjustability, and removal of the top compartment (AKA brain). Let’s dive in.

This pack is built with a UHMWPE ripstop grid nylon fabric. UHMWPE  refers to its ultra high molecular weight polyethylene, which is used in the rip stop grid, making it extra hard to tear, even if a small puncture should occur in the regular nylon.

The back panel and pre curved hip belt (with lovely reverse pull adjusters) are constructed with a very comfortable perforated foam with large air flow valleys to help reduce heat build up. The foam paneling is connected to a hour glass shaped spring steel pipe frame with load lifters up top to reduce shoulder pressure and transfer weight to the hips.

Traversing the entire lower half of the pack are a wide array of front and side pockets, made with more of the same ripstop nylon (and a bit of mesh). While generally voluminous, if the main body compartment is fully loaded, it eats into exterior pocket volume from the inside, reducing the amount of gear you have easy access to. Its hip belt pockets do not have structured undersides, meaning they feel a bit thin and act smaller than they look. An easy improvement to this pack would be adding a bit more slack to most, if not all of the external pockets.

A few other minor odds and ends caught our attention, including the top drinking bladder tube ports, which are a rain entry point. We also found the PackMod pockets to be lackluster. The shoulder strap mesh one is slightly too small for a full size phone and doesn’t seem very durable. Another hangs loosely and bounces around as you walk.

Top down view of REI Co-op Flash Air 50 Backpack for review
interior view of main compartment

Accessorize your REI Co-op Flash Air 50 Backpack

Like most backpacks, the REI Co-op Flash Air 50 is not inherently waterproof. While the exterior fabric is rain-resistant, we strongly recommended storing sensitive items, like your sleeping bag and down jacket, inside dry bags. You should also carry repair patches and proper bear storage.

close up on bottom front of pack
close up on back panel surface

Expanded Features Analysis of REI Co-op Flash Air 50 Backpack

Main Compartment: The ~40L main compartment is more than large enough to store an ultralight kit, and large enough to store a lightweight or moderate kit. Ultralight backpackers will have nothing to complain about size-wise. Bullseye, sweet spot volume.

Back Panel: The aerated foam back panel is comfy and reasonably breathable. This one gets good marks from us and is the exact same as what’s found on the Flash 55. No back panel can prevent sweat, all they can do is reduce it slightly.

Frame: The spring steel piping frame is in the shape an hour glass and does a decent job of transferring weight from the shoulders to the hips.

Fabric: This pack is built with a UHMWPE ripstop grid nylon fabric. UHMWPE  refers to its ultra high molecular weight polyethylene, which is used in the rip stop grid, making it extra hard to tear, even if a small puncture should occur in the regular nylon.

Shoulder Straps: The shoulder straps are medium thickness and reasonably comfy. But a couple of minor downsides include the lack of a daisy chain loops for attachable custom pockets, and the use of a sternum strap slider beam instead of a nylon webbing adjuster or daisy chain increments. Speaking generally (not specifically to this pack) sternum sliders are prone to falling off the beam, or moving around over the course of a day.

Front Pocket: This is a fairly nice front pocket, well-sized, and slightly better than the Flash 55’s. That’s because it has a cinch closure top, rather than a buckle. But like with the Flash 55, its volume is significantly decreased when the main compartment is packed full, and it would have benefited from a bit more slack. We also spot the side mesh panels, which decrease durability and increase liability, all for a bit of breathability/drainage. Not a worthwhile exchange in our opinion.

Side Pockets: The Flash packs have a unique side pocket configuration. The most interesting part is that there are two medium sized pockets per side, rather than one large pocket as can be found on most packs. The smaller of the two pockets is placed into the gap between the hip belt and normal side pocket position, using a space that would have otherwise gone to waste, so that’s smart. What’s more, these pockets are oriented forward so people with moderate to good shoulder mobility can reach back to access with out taking the pack off. If you have low shoulder mobility, you will still struggle to use these pockets. It may also feel weird as the bottle may contact your hips a bit as you walk. These pockets are sized for a 1L Nalgene bottle, and too loose for a 1L Smartwater.

The taller, more traditional side pocket, sized for a 1L Smartwater-shaped bottle, are very tall, and kind of slim. We wish they were a bit shallower, and a bit girthier. All said and done, Flash packs have a unique take on pockets, but we aren’t convinced it’s better than the traditional one-large-protruding-pocket system used on most ultralight packs.

Hip Belt and Hip Belt Pockets: The pre-curved aerated foam hip belt is comfy and nice, and the best part about it is that you probably won’t notice it much because it does its job well. It is the same design as is found on the Flash 55. The reverse pull buckles are easy to use and adjust on the go. While the hip belt pockets are sufficiently sized, we ding them slightly for not having lower gusseting to add volume (the bottom of the pocket is basically 2-dimensional/flat), while the top is wide and 3D. As such, they performer smaller than they look.

PackMod Accessories: Unfortunately, we’re not fans of REI’s PackMod pockets. The shoulder strap pocket is too small, and its mesh body is not durable enough. And the hanging mesh pocket bounces around as you walk and should be removed entirely.

pocket detail on rei co-op flash air 50
hip belt detail

REI Co-op Flash Air 50 Review Verdict

We’re ecstatic to have found a legit ultralight backpack from a mainstream brand. Flash Air 50 is large, light, and comfy. From price to performance, this one is really good across the board, albeit not exceptional in any particular way.

Compare to more great option in our guide to the best backpacking backpack.

empty back side of rei co-op flash air 50 pack
empty and flat view of pack