Gear Review: Women’s REI Co-op Flash 45 and 55 Backpacking Packs

The consensus? From handy hipbelt snack pockets, to removable top lids to adjustable-size water bottle pouches, these packs impressed the reviewers with their smart, customizable features.

Whether you want to travel super light or feel super comfortable, you’re going to need the right backpacking pack for your outdoor adventures. And you’ll want your backpack to work as part of a seamless camping system that includes your pack, shelter, sleeping bag, pad, stove and other essentials. Together, these items comprise your core backcountry camping kit. Enter the REI Co-op Flash series, where you can bring together a Flash pack, tent, tarp, sleeping bag, chair and more to equip you when you head into the backcountry.

The REI Co-op Flash 45 and Flash 55 packs are the newest additions to that series—and we were excited to test the women’s models in the mountains near South Lake Tahoe, Calif. The REI Flash 45 and 55 backpacks have a unique origin story. To decide how to build the packs, REI circulated a survey among its store employees, seeking feedback about how to address the needs of backpackers from a variety of backgrounds and geographic locations. As the team developed the packs, every new iteration was sent out and used in the field by REI employees for research and validation.

To do our own gear testing, we loaded up the Flash 45 and 55 backpacking packs for a winter ski tour in the Eldorado National Forest. Each weighed down with 30 pounds of gear and food, we skinned through 6 inches of fresh powder to reach our backcountry campsite by a frozen lake. With a combined eleven years of guiding and instructing experience between us, we’ve both worn countless backpacks over the years. While we both now work full time and co-parent our fluffy rescue dog, we still spend every spare moment in the mountains and were excited to test the Flash 45 and 55.

A woman standing on skis in a snowy forest with a heavy pack on her back.

The reviewers loaded the packs down with 30 pounds of winter gear for a backcountry ski tour in Eldorado National Forest. (Photo Credit: Shelby Carpenter & Caitlin Brown )

On this trip, we found both packs to be extremely comfortable and decked out with useful, removable and customizable features. Dubbed “Packmod,” these features include a removable lid, removable hipbelt and compression straps that are easy to move around. On the Flash 45, there are removable, easy-to-move compression straps that let you customize the pack and get it as compact as you need it to be.

On the Flash 55, the full host of Packmod features, including a removable lid, hipbelt and compression straps, allow maximum customization. It’s great to be able to remove these nice-to-have features if you don’t want them—if you don’t tend to carry snacks on your hipbelt, for example, you can always nix that feature on the Flash 55 for weight. Removing features can reduce the weight of the Flash 55 by nearly half a pound, meaning you can it for fast-and-light missions and standard backpacking trips.

Beyond these perks, we evaluated both packs with the following attributes in mind:

The bottom line: these packs are very comfortable for their weight and are perfect for someone who counts ounces, not grams, going out on a one- or two-night winter backpacking trip, ideally without a bear can. Although we didn’t test the packs in summer, with fewer bulky winter items, we could see using the Flash 55 for a four- to six-night backpacking trip and the Flash 45 for a two- to three-night trip by thoughtfully packing calorie-dense foods.

Weight and Comfort

The women’s Flash 45 weighs 2 pounds, 9.5 ounces, and the Flash 55 weighs 2 pounds, 11 ounces (but can be reduced to 2 pounds 4 ounces). On both packs, the hipbelt naturally contours to the shape of your waist and has foam padding and mesh that breathes well, even when you’re working up a sweat. We were impressed at how comfortable the hipbelt on the Flash 45 was; many packs in this size range don’t have hipbelt padding, since backpackers typically use packs of this size for lighter loads that don’t require as much support. However, the foam and mesh on this pack made it comfortable to carry up to 35 pounds.

As with the hipbelt, the back panel on both the Flash 45 and 55 features a foam-mesh combo that hugs your body while allowing air to flow. Whereas packs made by other manufacturers sit further off your waist and hips due to their unique, mesh-based suspension system, the Flash sits close to the curve of your back. We found this to be quite comfortable, and we wouldn’t want a pack that sits further off our backs for something like climbing or skiing, where full-body movement and dexterity is so important.


The Flash 45 and 55 are examples of a simple suspension system done right. The load lifter straps are easy to reach—even with mittens on—so you can adjust to carry more weight on your shoulders and/or your hips. The foam and mesh back panels, shoulder straps and hipbelts provide cushion to help you carry weight with comfort. The sternum strap is easy to adjust; and you tighten the hipbelt straps by pulling inward rather than outward, making them a cinch to tweak on the go. 


Both the Flash 45 and Flash 55 come with the aforementioned customizable Packmod accessories—straps and components you can move around on your pack, or remove for weight savings. The Flash 55 has a removable top lid, and both packs feature Packmod compression straps that can be girth-hitched and that reach between two daisy-chain like cords running down the exterior of the pack. The straps can be used to shape the load of your pack, compressing items and bringing them closer to your back so the weight of the pack doesn’t throw off your center of gravity.

Packmod Features on the Flash 45 and 55 Packs

Removable Compression Straps Removable Top Lid Removable Smartphone Pocket Removable Hipbelt Pockets
Flash 45
Flash 55

In addition to the Packmod straps, the Flash 55 comes with additional customizable features—most notably a removable smartphone pocket that attaches securely to your shoulder strap. While we could fit Caitlin’s iPhone 6s in a protective case in the pocket, we could not fit Shelby’s larger iPhone XR, also in a protective case. This pocket will work best with small phones or phones with low-profile cases.

Unlike with the Flash 45, the Flash 55’s hipbelt pockets are removable. To cut weight, you can remove the Packmod accessories from the Flash 55, reducing the pack weight by 7 ounces. On the 45, you can remove the compression straps to cut weight, but you can’t remove other features. 


When Caitlin was an Outward Bound instructor, she taught her students the ABCs of packing: accessibility, balance and compactness. When packs have too many compartments, they grow unwieldy, causing hikers to feel off-kilter on the trail. With too few compartments, a backpack can turn into a black hole. Both the Flash 45 and 55 struck the right balance.

The Flash 45 and 55 each have one main compartment, a brain, hipbelt pockets, three exterior mesh pockets and two open side pockets. The main compartment has a liner for stashing a hydration bladder. The large exterior mesh pocket was perfect for stowing a shovel; it would also work well for rain gear or maps. There is a small, expandable pouch on the sides of both packs next to the water bottle pocket that easily held a foam sit pad and an avalanche probe secured higher up on the pack with the side compression straps. The brain was large enough to hold a SPOT satellite messenger, sunglasses case, toiletries and headlamp.

Additional Features on the Flash 45 and 55 Packs

Hydration Compatible Main Compartment 3-D Contoured Hipbelt Water Bottle Pockets Exterior Side Pockets Breathable Mesh Front Pocket Roll-Top Closure
Flash 45
Flash 55

We particularly appreciated that the water bottle pockets could securely hold a variety of bottle sizes due to a nifty snap closure that secured the pocket tightly around smaller bottles. Neither of us had seen something like this on a pack before, but we certainly hope to see more in the future. Finally, the zipper pulls on the lid and hipbelt pockets were large and glove-friendly (and removable for gram-counting summer backpackers).

A close-up shot of a backpacking pack weighed down with gear on the back of a woman in the snow

The large exterior mesh pocket on Flash 55 is perfect for stowing a shovel; it would also work well for rain gear or maps. (Photo Credit: Shelby Carpenter & Caitlin Brown)

While the body of the Flash 45 is topped off by a quick-draw pull string, the Flash 55 features a roll-top closure that you secure with buckles. Although the packs aren’t technically waterproof, this is a nice benefit for rain protection. It did, however, seem as though a lot of the additional capacity in the Flash 55 came from this feature. We were a bit concerned that the pack could get top-heavy since this design encourages users to continue packing up and up, and we would have preferred to see the pack have a wider fit for more storage. 


Caitlin used the Flash 45 to carry her gear, food and our shared stove (to relieve our tired pup, she also carried a dog backpack strapped under the lid on the way back and can confirm that the Flash 45 is fully compatible with the Ruffwear Palisades dog pack). However, some users might find it difficult to carry a bear canister while using this pack. Provided you aren’t in bear country or a companion can carry the bear can, this pack offers enough capacity for most one- to three- night trips. The two hipbelt pockets were also a solid addition and easily held snacks, hand warmers and an iPhone 6s.

In the Flash 55, Shelby carried a larger load with a bulkier, three-person tent (perfect for two people plus a dog). The Flash 55 fits a BearVault 500 vertically and would work for a multi-day trip with a bear can and minimalist gear.


If you look good, you feel good. And if you feel good, you can go longer, farther and harder. We appreciated the gender-neutral color options for these packs. The Flash 45 comes in Castlerock (aka neutral gray) and Pumpkin (aka red-orange) and the Flash 55 comes in Seattle Mist (aka gray) and Olive Oil (aka greenish-yellow). No “shrink it and pink it” here! The packs come in both women’s and men’s versions, and while the product specs don’t include details on what makes the women’s packs different, we can say that we both felt the hipbelts contoured comfortably around our hips to carry weight well and the sternum straps were well-positioned for us. 

The verdict

These packs both went through multiple stages of field testing—and it shows. It’s clear they were designed with an eye toward allowing backpackers to make modifications according to their needs. On the Flash 55, we’d like to see a larger Packmod pocket available for a phone and a design that is a bit wider. A wider pack would move the load down towards the small of the back, and the Packmod straps would still allow compression if carrying a smaller load.

Both packs carry weight comfortably, and we wouldn’t change a thing about the hipbelts or suspension system. From the snack pockets on the hipbelt, to the removable top lids to the adjustable-size water bottle pouches, these packs impressed us with their smart, customizable features. We’d happily use them on outdoor adventures again in the future.

Shop the REI Co-op Flash Series