Main compartment holds a 2-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 Airflow padded back wicks moisture. Vapel mesh Airflow adjustable shoulder straps * Reflective loop holds a bike LED blinker. * Size: 14.5" x 0.0" x 10.5" Capacity: 100.0 cubic-Inch Weight: 1.07 lbs. Materials: Waffle Weave