Description: Hydration vest backpack: This running vest features a compartment at the back that can accommodate a 2 L water bladder (not included), allowing you to hydrate quickly while running. It is suitable for medium to long distance runningMaterial and packaging: This hydration vest is made of polyester, lightweight, and comfortable to wear. The package includes 1 running hydration vest, equipped with 2pcs 500ml TPU soft water bottlesComfortable wear: This water backpack adopts an ergonomic design, along with adjustable chest straps for a snug fit, making it comfortable to wear and easy to put on and take offLarge capacity: This hydration pack comes with 10 pockets at the front, convenient for storing water bottles, keys, and other daily items. It offers large capacity storage while ensuring easy accessWide application: This water pack is nice for various activities such as running; hiking; cycling; backpacking trips; mountain climbing, etc Specification: Material: Polyester and TPUWater Bottle Capacity: 500ml Size Chart: S: Length: 44cm/17.32inch; Chest: 78.5cm/30.91inch; Suitable for Chest: 78cm-86cm/30.71inch-33.86inch;M: Length: 45.5cm/17.91inch; Chest: 83.5cm/32.87inch; Suitable for Chest: 87cm-92cm/34.25inch-36.22inch;L: Length: 47cm/18.50inch; Chest: 88.5cm/34.84inch; Suitable for Chest: 93cm-99cm/36.61inch-38.98inch;XL: Length: 49cm/19.29inch; Chest: 93.5cm/36.81inch; Suitable for Chest: 100cm-107cm/39.37inch-42.13inch;2XL: Length: 51cm/20.08inch; Chest: 98.5cm/38.78inch; Suitable for Chest: 108cm-120cm/42.52inch-47.24inch; Package Includes: 1 Hydration Vest,2 Water Bottles Note: Please allow slightly errors 1-2cm differences due to manual measurement.