Altosy 3712 Classic Sport Hydration Pack with 2l Hydration Bladder nylon Imported Full-length main pocket with hidden zipper& weather guard,which can keep warm of the water in water Large main compartment holds a 2-liter water reservoir. Easy-access reservoir opening is easy to fill and accepts most brands of water filters. Vapel mesh Airflow padded back wicks moisture. Vapel mesh Airflow adjustable shoulder straps. Adjustable waist belt secures the pack. Adjustable waist belt secures the pack. Reflective loop holds a bike LED blinker Zippered front accessory pocket holds bicycle tools, accessories, or CD/MP3 player. Mesh front pocket can holds a helmet. Material: High quality waterproof Size: 17.32"x11"x6"