Saming 3L TPU Hydration System Bladder Water Bag Pouch Backpack Hiking Climbing Black Two layers cargo design, one for hydration bladder, and the other for extra carrying purpose. Equipped with a tube with a bite valve to drink, so you don't need to hold it to drink. Perfect to use when hiking, climbing, riding and other outdoor activies. Adjustable shoulder strap and chest belt, suitable for heavy carrying. Constructed by waterproof 600D high density Nylon material.