Osprey Packs Exos 58 Backpack Synthetic An internal sewn-in backpanel sleeve with clip attachment accommodates up to 3 liters of hydration and Fabric-main 100d high tenacity nylon,accent 100d high tenacity nylon ripstop bottom 100d high tenacity nylon ripstop The Exos peripheral frame is a 6065 aluminum alloy with an internal suspended cross strut providing excellent load carrying support. The ExoForm sewn-in, EVA foam padded harness combines breathability and performance with seamless layered mesh The ExoForm sewn-in hipbelt features seamless layered mesh covered foam providing exceptional comfort A removable floating top pocket with an internal key clip and under-lid zippered mesh pocket provides organization