Description: High Capacity and Comfort: This Hydration Pack is a lightweight, breathable backpack, features a double stability system for comfortable wear during outdoor activities like cycling, running, or hiking.Storage Design: The shoulder backpack storage can hold soft water bottles, energy gels, or other supplies. There's also a zippered compartment on the shoulder strap for small items like cards, phone, etc.Quality Material: Cycling bag water bag is made of polyester fabrics, waterproof, lightweight, thin, comfortable, quick drying, and resistant to wear and tear, making it great for long outdoor adventures.Reflective Design for Safety: The hydration backpack has a reflective design that enhances visibility in low light conditions, and equipped with a safety whistle, making it for night time activities. Size: 38x20x10cm/14.96"x7.87"x3.94".Multifunctional Use: Additionally, there are external hanging devices where you can hang warning lights; it also has a mountaineering stick mounting device with an elastic rope design for stable carrying without shaking. Specification: Material: PolyesterSize: 38cmx20cmx10cm/14.96inchx7.87inchx3.94inch Package Includes: 1 Hydration Backpack2 450ML Hydration Bladder Note: Please allow slightly errors due to manual measurement and different monitors.