Nathan Zelos 2-Liter Hydration Vest, Nathan Grey, One Size Equipped with one 18oz/535 ml SpeedDraw flask in right pocket Two front bottle pockets and one front zip smart phone compatible pocket Rear external shock cord for increased capacity Newly engineered 3 way propulsion harness stabilizes side to side and up and down movement of bladder Bounce free ride keeps items in the storage pockets and hydration stable