Large Capacity: Features on a mian compatment storing max. 2L water bladder(not included),a front open pocket,two side drawstring pockets and two small side zipper pockets. Lightweight & Breathable: (Only 0.5 lbs) Made with lightweight polyester materials for durability. Excellent air ventilation system consist of mesh back and adjustable wide mesh shoulder straps,prevents stuffiness and distributes weight effectively.And flexible sternum straps reduce strength consumption. Convenient: The hydration backpack with two sides water outlets,easy to drink water without taking the backpack off or stopping your steps.Convenient whistles for enmergency sistuations. Safe: Reflective strips around the bag provides more safety during nighttime activities.