The ergonomic backpack is suitable for travel,hiking,cycling,running,climbing. Features: Made of lightweight tear resistant polyester fabric,and integrated breathable mesh pad on the back. 20L loading capacity with multiple pockets is large enough for daily needs such as clothes,purse,keys,books,phone and umbrella etc. The lightweight fixed steel ring is designed to support the backpack to distribute weight effectively,breathable and comfortable. Ergonomic shoulder straps,adjustable waist belt and flexible sternum strap reduce strength consumption. Equipped with a water bladder compartment for 2L water bladder.(The water bladder not included.) With invisible mesh net,you can hold your helmet easily on the backpack during activities. Reflective strips around the backpack are more safer when you riding or running at night. Specification: ColorBlack/Blue/Red/Green (optional) Material: polyester Capacity: 20L Package weight: Approx. 900g/31.7oz Package List: 1* Backpack