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.