The Ultra 4 Hydration Vest is CamelBak's most versatile vest for running roads, trails, and anything you set your feet on really. This vest has the capacity for longer runs, including space for water bottles, layers, gloves, keys, hat, phone, and nutrition. The cargo compartment expands so you can fit more items than this list. CamelBak included a 2L Antidote reservoir with an easy to open Quick Link system, HydroGuard antimicrobial technology, Big Bite Valve, and PureFlow tube. The Ultra 4 Hydration Vest has external fill capability that allows you to refill while running. CamelBak made this vest with reverse chain nylon for durability, padded mesh for breathable comfort, and open mesh at the shoulders to ensure proper ventilated airflow throughout all your marathons.