Get the REI Co-op Women's Flash 55 Pack for $139.29 (Save $59.71) Get the Patagonia Women's Nano Puff Insulated Hoodie for $148.93 (Save $100) Get the REI Co-op Men's Stormhenge Down Hybrid Jacket ...

The travel-ready REI Co-op Flash 18 Pack shines at just 9.5 ounces with its great pockets, 18 liters of space, fun colors, a hydration sleeve.

We tested two of the most popular backpacking backpacks — the REI Co-op Flash 55 Pack and the Osprey Aura AG — to figure out which is better for your next hike.