Seamand 3L Hydration System Water Bag Pouch Backpack Bladder Climbing Hiking It's constructed by waterproof 800D high density Nylon material Two layers cargo design,one for hydration bladder,and the other for extra carrying purpose Adjustable shoulder strap and chest belt, suitable for heavy carrying 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 actives.