Zero fluid bounce boa dials on either side of the pack compress a 2 litre h2orizontal reservoir to the runner39s back ensuring no sloshing perfect fit the ultimate in perfect fit race vests it molds to upper body delivering supreme comfort race ready comfortably holds all mandatory kit includes soft cup and emergency blanket both kit requirements for ultra races including utmb use on the move all pockets including a large external pouch are easily within reach meaning kit and foo