High Sierra Expandable Hydration Pack (Green & Grey) Main compartment with special thermo-silver insulation, holds a 2 littler /67.6 once reserviuor and has a bicycle pump sleeve SOURCE WideSlide anti-microbial reserviour has a wide opening for easy filling and adding ice SOURCE Z-VALVE Hydration bite valve and built-in SOURCE DOCKING STATION to keep tube in place when not in use Insulated water tube cover prevents water from freezing in the tube Zippered expansion gusset for increased capacity