As a travel writer who specializes in outdoor adventures and national parks, my hiking backpack game is strong. When I’m not trekking across Patagonia, I’m likely road-tripping across the Olympic Peninsula or hitching a Jeep ride in rural Nepal. I’m constantly searching for the perfect bag that can perform well across a wide variety of adventures.
A bestseller I’m constantly seeing in town and on the trail, REI Co-op’s Flash 18 Pack, has always stood out to me as one of the lightest, best-designed backpacks on the market today. I’ll likely own some version of it for many years to come too. Not only do I never think twice about tossing it into a larger suitcase or duffel (the thing weighs a measly 9.5 ounces) but it’s shockingly full-featured for a bag costing $50.
Boasting a hydration sleeve, hip belt, zippered pocket and a padded back panel that doubles as a sit pad in wet conditions, this backpack offers plenty of the bells and whistles of a pricey name-brand pack at a fraction of the cost. Below, I’ll explore what makes this pack a true standout and my go-to for shorter day hikes, summit bids and international adventure trips.
Surprisingly full-featured for its scant 9.5-ounce weight, REI Co-op’s bestselling Flash 18 Pack offers great pockets, a sit pad, a hydration sleeve and a hip belt in an ultra-slim design that’s affordable and can pack down easily into a larger backpack or suitcase.
What I liked about it
The Flash 18 Pack manages to cram a lot of great features into one petite package. Its packable design, good pockets and ultra-light weight are just a few reasons why I love it.
Ultralight and packable
At a slim 9.5 ounces, the Flash 18 Pack is one of the lightest day packs you’ll find in stores. Take away its removable sternum strap and hip belt and you have a 7.7-ounce go-anywhere bag. It’s a thin backpack that won’t easily snag when bushwhacking in the wild, as it’s constructed with 70-denier recycled ripstop nylon and a nonfluorinated durable water repellent (DWR) finish.
I recently took a four-day-long weekend trip to Oakland and could easily fold the Flash 18 Pack into my (already stuffed) Patagonia Black Hole duffel, which I used as a carry-on. Then, once I hit the town, I didn’t have to lug around my bulky 45-liter bag; I could wander freely with a small daypack for my snacks and layers.
Functional pocket design
Because of its large, open, single-pocket design, REI’s Flash 18 works well for various activities. Back when I was learning to mountaineer in the Eastern Sierra, I would often toss this tiny bag into my larger 60-liter backpack and use its outer webbing and ice tool loop for quick summit attempts, right out of base camp.
On the outside of the Flash 18 is a hidden, zippered pocket that is perfect for small items like a wallet, a set of keys, a protein bar or some lip balm. Inside, you’ll find two non-zippered slip pockets, ideal for stowing additional snacks or trekking poles when they’re not in use. There’s also a hydration sleeve with an exit port for your bladder’s hose, plus a hang tab so it doesn’t jostle on your more rugged excursions.
Yet another reason the Flash 18 Pack is an excellent travel companion is that it instantly turns into a stuff sack or organizational pouch within a larger bag or suitcase. Simply flip the Flash inside out and cram it full of your underwear or dirty laundry.
Fun extras
As mentioned, this little marvel is astonishingly feature-packed despite being both compact and budget friendly. Exterior loops on the pack’s outer layer make it easy to attach a cord and strap on wet outer layers or an ice tool. A hip belt and sternum strap help create a more comfortable carry too. The pack’s back padding is also removable so it can turn into a sit pad, and the Flash’s quick-pull cinch tab up top is easily accessed with a single hand or even in cumbersome mittens. But best of all, the Flash 18 Pack comes in fun, high-visibility prints and colors (including a special series for Pride Month) so you can express your wild side on the trail.
What I didn’t like about it
Of course, there’s no way a 9.5-ounce backpack that folds up and fits into your pocket has everything on my list. Below, I’ll get into a few things this little wonder lacks.
No interior security pocket
Call me old-fashioned, but I prefer to put do-not-lose items like my keys and wallet inside my backpack so there’s no way I could drop them when I’m trail running, biking or hiking. This is also my go-to strategy when traveling through a new city, especially when I might not know what areas are rife with pickpockets. Unfortunately, REI Co-op’s Flash 18 only has two interior slot-style pockets, no zippers included. As such, I tend to put my keys in the outer pocket and hope for the best.
Could be more comfortable
It makes sense that at 9.5 ounces, you don’t get a pack with cushy shoulder straps and a thick, padded hip belt. Sure, REI Co-op has done pretty much everything in its power to give the Flash 18 a decently comfortable carry, like designing breathable mesh shoulder straps, including a sternum clip and lightly padding its back, but it’s never going to hold 20 pounds in a comfy position on an all-day hike. Based on my experience trekking through Sequoia and taking weekend trips with this baby, I’d recommend it for loads of 10 pounds or less.
How it compares
Considering that REI Co-op’s fabulous return policy backs the Flash 18 Pack and that it costs a wallet-friendly $50, it’s an affordable and reliable pick for anyone who needs a lightweight, packable day bag for travel and hiking. If you’re looking for more storage space, check out the REI Co-op Flash 22 Pack, which has a thicker hip belt, a top “brain” pouch and exterior water bottle pockets.
If you love bright colors and don’t mind spending a little extra on a brand with a stellar environmental track record, Cotopaxi’s Luzon 18L Backpack weighs a scant 10.6 ounces and has a design similar to the Flash 18.
Lastly, if you’re a die-hard Osprey fan (I love its All Mighty Guarantee), its 20-liter Daylite Plus Pack is made with thicker, more durable recycled ripstop polyester than the Flash and has both compression straps and water bottle pouches on its exterior. If you intend to carry a heavier load, the Osprey Talon 22 Pack is a more heavy-duty day pack that can comfortably take up to 20 pounds in its compartments while boasting a thicker, pocketed hip belt; a helmet carry; and additional storage pockets. But it does cost significantly more than the Flash 22.
Bottom line
Ideal for good-weather day hikes and airplane travel (when you need a day bag but only want to bring a carry-on), REI Co-op’s Flash 18 Pack is one of the lightest, most packable backpacks on the market. It wowed us with its low price of $50, its thoughtful pocket and strap design, and adorable colorways. I think it’s a must-have when space and weight are at a premium.
