The High Sierra Wave 50 Hydration Pack's main compartment holds a 1.5-liter water reservoir. Easy-access reservoir opening is easy to fill and accepts most brands of water filters. Hands-free reservoir pressure valve. Insulated water tube cover prevents water from freezing in the tube. Zippered front accessory pocket holds smaller items such as keys, a wallet or a cell phone. Vapel mesh AirflowTM padded back wicks moisture. Vapel mesh AirflowTM adjustable shoulder straps. Reflective loop holds a bike LED blinker.