REI Flash 18 Pack

Lightly padded stretch-mesh shoulder straps enhance comfort
Removable back panel pad doubles as a sit pad
Hipbelt and sternum strap can also be detached
Sternum-strap buckle doubles as a safety whistle
Hydration-compatible design includes a hose exit port and an internal sleeve for a reservoir (sold separately)
Drawcord closure fully covers the top opening when cinched tight
Pack has an inner zip pocket and 2 daisy chains outside