Totally PracticalityThere is a spacious master cabin with a built-in 3L replaceable bladder that allow you to carry your water conveniently.Another number of internal pockets are smart phones, pencil bags and so on,External zip pocket save small accessories as keys, etc.High Quality MaterialThis hydration pack measures 17cm 4cm 44.5cm (6.69in 1.57in 17.51in) .Made of ultralight waterproof tear resistant nylon fabric,designed to keep you cool and dry while on your outing.Very attractive,comfortable and durable.Adjustable StrapsBearing system with breathable material, adjustable padded shoulder straps for comfort, chest strap and waist strap to fit your need.Must Equipment for Outdoor SportsThe mini Cycling Rucksack has ergonomic design on the back for maximum breathability and comfort. Lightweight suitable for outdoor activities like outdoor, running camping mountain climbing, hill walking, cycling, rock-climbing and hiking, etc.