Description: 【Material and Comfort】: This running vest is made from nylon, featuring a lightweight breathable mesh panel. It is highly flexible, comfortable, making it great for running training, hiking, and marathons. 【Hydration Capacity】: The vest comes with 2pcs 450ml hydration bladders made from TPU materials. This ample water storage capacity meets the hydration needs of outdoor activities. 【Adjustable Fit & Features】: The hydration backpack has adjustable straps to fit your size perfectly. It also features reflective stripes that glow at night ensuring safe running or cycling after dark. 【Storage Space】: The running vest offers enough pockets to store your essentials like mobile phones, keys, rain jackets, water bottles, hydration flasks, bladders, etc., during outdoor activities. 【Versatile Use & Compact Design】: Designed for road biking, running, hiking with a compact structure that keeps your back stable without creating much wind resistance. Specification: Material: Nylon, TPU Size Chart: Backpack: 39cmx21cmx18cm/15.35inchx8.27inchx7.09inch Bust: 72cm-110cm/28.35inch-43.31inch Water Bladder: 27.5cmx9.5cm/10.83inchx3.74inch Package Includes: 1 Hydration Vest, 2 Water Bladders Note: Please allow slightly errors 1-2cm differences due to manual measurement.