Osprey designed the new Aether Backpacks with a brand-new fitting system-Osprey's best-and the Aether 55 Backpack is perfectly sized for weekenders and overnighters. The back torso adjusts vertically to customize the fit for all sizes, and On-the-Fly shoulder strap and waist belt adjustments ensure quick-and-easy micro-adjustments that you can cinch on the trail. Osprey not only integrated a rain cover, but also treated the main fabric in DWR in case you don't get the cover on in time. A LightWire frame offers surprisingly stiff rigidity when you're carrying heavy loads, and Airscape mesh provides breathable ventilation on your back.