A different take on an ultralight backpack, the Arc’teryx Aerios 45 Backpack features a very strong, durable, and waterproof fabric that’s combined with a unique zone-reinforced framesheet that’s lighter than a conventional internal frame but offers good load-carrying comfort and terrific torsional and longitudinal stability. Lots of pocket storage options on the shoulder straps and hip belt (including a running vest-style approach to the shoulder harness). Side pockets are huge and easily accessible while wearing the pack. Roll-top closure can remain closed while contents are accessed on the fly through a vertical waterproof zipper into the main compartment.