This hydration rucksack has a capacity of 6L, iincluding a compartment that will allow you to carry a 1.5L water bottle. The rucksack has been designed to fit snugly around your body so that you do not have to stop if you wish to have a drink. It is ideal for walking, biking and skiing. It is lightweight and durable and has reflective trims for added safety in poor light.