Aqua Arm Hydration Pack 2.0 for Running - Running, Cycling, Walking, Hiking, Trailrunning, Hydration System, Water Bladder Reservoir, Sport ES Short, lightweight, non-chafing, designed for comfort-in-motion specifically for runners. Holds up to 18 oz. of liquid hydration. Front pocket for cell phone, keys, credit card or mp3 player. Integrated thermal layer, keeps liquid cold. Sport ES Approved, Fits Women & Men.