Product description Size: 43*18*23cm Color: sky blue, rose red, black Material: Oxford cloth EVA, PVC Package content: 1pcs outdoor backpack 1pcs outdoor sports water bag 1. LIGHT & COMFORTABLE: With the adjustable shoulder / chest / waist straps, the hydration pack adapts to any body size and the ergonomic design and breathable material ensure high wearing comfort for men, women and young people. 2. RELIABLE: Thanks to premium nylon material, our bike backpack is robust. The splash-water-repellent material keeps your things dry and clean in light to moderate rain. Reflectors and integrated signal whistle ensure a high level of safety. Suitable for outdoor activities such as cycling, running, hiking, climbing, etc. 3. WONDERFUL SPACE : Bike backpack was designed with a main compartment for a 2L hydration bladder, a small pocket for small things such as a smartphone, keys or two cereal bars, and an elastic band for sun protection clothing and towels. 4. INTERCHANGEABLE 2L BLADDER: The supplied 2L hydration bladder uses FDA-approved BPA-free material and has an enlarged screw cap that makes it easier to fill with liquids. Perfect for filling with ice cubes or various sports drinks. The bladder's internal airflow system is heat insulating and provides you with cool water all the time on the go. 5.SAFETY IN MIND: Reflective safety tabs and reflective logo for high-visibility in low-light environments, keep you safe and hydrated for most extreme environments & weather conditions, use food grade material for the bladder.