Small, Simple, and Shockingly Capable: REI Co-op Flash 18 Daypack Review

I jogged up to my ski partner’s truck, ready to get some August turns in, only to be met with uncontrollable laughter. That’s the reaction I got when I showed up with my ski blades and boots clipped to the outside of my REI Co-op Flash 18 ($40) pack, like some pro-backcountry skier ready to hike and slash K2.

But I quickly learned how capable this little daypack really is. From summer skiing missions to steep mountain hikes and even just zipping around town on my bike, the Flash 18 proved itself as a surprisingly versatile companion.

Despite its small size, this pack is loaded with hidden tricks. The Flash 18 can be flipped inside out to serve as a stuff sack, the removable back panel doubles as a camp-ready sitting pad, and the many exterior attachment points let you carry far more gear than you’d expect from an 18-liter backpack.

I put the Flash 18 through the wringer during a summer full of adventure on Colorado’s Western Slope, and with every mile and mission, I found myself reaching for it again and again.

In short: The little REI Co-op Flash 18 is a daypack fit for most outings on the trail. It’s perfectly sized for single-day hikes, or can be packed in with your backpacking kit as a stuff sack and deployed once you’ve set up base camp. There isn’t much in the way of a built-in suspension system, complicated organizational systems, or the ability to carry a water bottle externally, but for the minimal spend, you won’t miss those features much at all.

Looking for a new bag to carry your essentials? Check out GearJunkie’s Best Daypacks Buyer’s Guide for more of our favorite options.

REI Co-op Flash 18 Daypack: Review

A Longtime Staple

The year was 2018 (maybe 2017?), and I was a freshman at Western Colorado University, eager to hit the trails and local climbing crags with friends. There was just one problem: I didn’t actually own a proper daypack. Sure, I had a backpack for textbooks and my laptop, but nothing technical or outdoorsy enough for hiking.

Somehow, I ended up with the REI Co-op Flash 18. Maybe it was the muted purple color, the sleek design, or, honestly, it was probably just the cheapest option I could find.

What I do know is that this pack quickly became a trusted companion. I carried it on countless bike rides, hikes, and even climbing trips in the Black Canyon of the Gunnison National Park. Years of heavy use later, I still have it, and it’s still going strong.

So why share this story? Because when a company gets a product right, it doesn’t need to reinvent the wheel; small updates and new colorways are often enough. That’s exactly what REI has done with the latest version of the Flash 18.

While the new Flash 18 stays true to its predecessors, thoughtful tweaks and added features have made it an even more versatile and capable pack than before. 

Made for Any Excursion

The Flash 18 from REI proved itself ready for just about anything during my summer adventures. I carried it on sunrise hikes with my camera in tow and even brought it along on an August skiing mission in the high country of Crested Butte.

What impressed me most was how adaptable the pack is — each excursion revealed new features that made life easier. When hauling ski blades, the hip belt helped distribute the weight and kept the pack snug against my torso. On long hikes, the exterior loops easily accommodated my trekking poles, keeping them within reach without interfering with my stride.

One of my favorite aspects was how perfectly the pack held my camera cube during sunrise photography sessions. Everything I needed for capturing those critical shots fit securely, with quick access when timing was everything.

From high-alpine skiing to early-morning hikes and casual adventures around town, the Flash 18 consistently proved itself as a lightweight, versatile, and surprisingly capable daypack.

Durability & Construction

The Flash 18 is a frameless daypack crafted from 70-denier, Bluesign-approved, recycled ripstop nylon and treated with a durable water-repellent (DWR) finish. The shoulder straps feature a padded mesh to help wick sweat and keep moisture at bay when temperatures rise, or rain begins to fall. Throughout the miles of use, I found that my shoulders never developed any hot spots, thanks to that added design element.

Weighing just 9.5 ounces fully loaded, the pack drops to roughly 7 ounces when you remove the hip belt and extra straps, making it impressively light for its versatility.

The Flash 18 has a straightforward bucket-style silhouette with a drawstring top and an additional fabric flap that helps seal out weather. Durable webbing is used throughout as a tool loop, waist and chest straps, and a hanging hook, adding functionality without significant weight.

During my testing, the ripstop shell and webbing held up well despite being thrown around, brushed against bushes, and hung from trees during breaks. That said, one of the side cord loops did tear when I clipped heavier gear to it via a carabiner, so it’s worth being mindful of how much weight you attach to the exterior loops.

Bells & Whistles

What really sets the Flash 18 apart is just how much it can do for such a small daypack. From the moment I started using it, I noticed there’s far more to this pack than meets the eye.

For starters, all of the extra webbing and straps can be removed or tucked away for a lighter, more minimalist setup. This is especially handy if you want a single pack for both outdoor adventures and daily commutes to the office.

The inner compartment padding, something my older Flash 18 even includes, can be removed from the sleeve and used as a comfortable sit pad during mid-hike breaks. That same padding also makes carrying firmer gear, like a metal water bottle or tent poles, much more comfortable on longer treks.

As the section title suggests, the Flash 18 includes a whistle on the shoulder strap for emergencies. While I didn’t need it for crises, it made calling my dog during hikes far less exhausting on my voice.

Perhaps the cleverest feature is that the pack can be turned inside out to serve as a stuff sack for use in a larger backpack or duffel. This came in especially handy during summer backpacking trips, since I’m notorious for misplacing sleeping bag stuff sacks.

All of these thoughtful elements combine to make the Flash 18 a one-stop-shop daypack that punches well above its weight.

Compartments & Pockets

The REI Co-op Flash can accommodate 18 L worth of gear on the inside. This is plenty of room for a water bottle, layers, snacks, and even a DSLR camera if you’re a photographer like me.

Additionally, the extra gear clips allow you to attach plenty of necessities to the outside of the pack and can even be used to attach the Flash to another larger backpack if you need the extra storage space. 

The Flash 18 has a larger main compartment, an inner sleeve for a water bladder or small laptop, two small non-zippered internal pockets, and a hidden zippered pocket located near the back panel for stashing your keys, phone, wallet, and much more. And within that pocket is another small, unzipped pocket, especially handy for smaller items. This thoughtful layout makes the Flash 18 surprisingly easy to organize despite its compact size.

Room for Improvement

While the REI Co-op Flash 18 is an affordable and reliable daypack, there are a few areas where it could be improved.

As mentioned earlier, one of the exterior loops tore during testing when I had gear attached via a carabiner. My older version of the Flash 18 featured a webbed daisy chain that held up well under similar use, so reinforcing these loops or using webbing could make them more durable.

Though I appreciate the minimalist exterior, a dedicated water bottle sleeve would be a welcome addition. When carrying liquids alongside a camera, quick access and spill prevention are important, and a side sleeve would make grabbing a Nalgene or bottle much easier.

Additionally, the tail webbing on the shoulder straps lacks fasteners, allowing it to hang freely while wearing the pack. Loose webbing can be annoying on the trail and presents a risk of catching on branches.

Even with these minor issues, the Flash 18 remains an impressive, versatile daypack that performs well in a variety of situations.

Value

At $40, the REI Co-op Flash 18 is a remarkable value, especially considering its versatility and thoughtful design. Many daypacks on the market start around $65 and can easily climb to $200 or more, making the Flash 18 a true diamond in the rough.

Its fully adjustable straps, removable padding, and ability to transform into a durable stuff sack add functionality that far exceeds its price. The pack’s adaptability makes it suitable for a wide range of outdoor adventures, from hiking and biking to summer skiing missions and casual daily use.

Additionally, the Flash 18 accommodates a wide range of body types, fitting torsos from 15 to 21 inches and waists from 26 to 42 inches, making it a versatile gift for friends or family who love spending time outdoors. For a sub-$50 daypack that can handle everything from trail outings to city commutes, it’s hard to find a better value.

REI Co-op Flash 18 Daypack: Conclusion

The REI Co-op Flash 18 Pack is perfect for anyone looking to buy their first hiking pack, especially if you’re on a budget and aren’t sure where to start. With 18 L of storage, it easily holds day-trip essentials like water, food, sunscreen, a phone, wallet, small camera, layers, and more, thanks to its extra capacity provided by the exterior gear clips.

If you don’t plan on taking it on extreme multiday excursions or have limited storage space, this pack is an excellent “do-it-all” option. It can double as an overnight bag for hostels, a laptop bag for work, or even a personal item on your next flight.

With its $40 price tag, tasteful colorways, and wide adjustability, the Flash 18 is a versatile, affordable choice for anyone in need of a reliable daypack that can handle both outdoor adventures and everyday use.