Nylon/Polyester 【Highly Durable & Lightweight】This awesome running hydration vest backpack made of scratch-resistant and wear-resistant material with a lotus leaf-like waterproof effect. 16.92”x8.66”x7.87” in size, Ergonomically fits, The weight of 0.97 lbs and capacity of 18L are the perfect match for short trips, satisfy your thirst for adventure. 【Premium Quality Water Bladder】The Hydration Pack Backpack comes with a 2 liter hydration water bladder and two 250ml soft flask. A switch valve and a cover cap make double leak-proof. Large opening allows quick filling of water and ice and it is easy to clean, the water line (40"length,0.4"diameter) provides a wholesome flow for easy drinking keeps your water tasting fresh, all day. The water temperature is range -20~+50℃. 【Security and Multiple Storage Pocket】Water backpack for hiking Reflective trim for night safety, has multiple pockets can store various necessities outdoor. The bottom front pocket allows you to quickly find what you need during hiking. Smaller quick access items without removing the pack, such as keys, wallet, gadget, sunscreen, phone, towel, or any other items. To travel light, efficient access, let you run faster and farther. 【Comfortable Back System】Lightweight cycling backpack Back lining and shoulder straps are all made of lightweight, breathable mesh fabric speeds up air-flow which can keep your back dry and comfortable while hiking. Soft shoulder strap edges prevent the pack from chafing your skin. Adjustable chest straps and waist straps can reduce the burden of shoulders make a backpack perfect fit reducing bounce and keep the balanced.