Nathan Men's VaporKrar 12LDeveloped with the demanding specifications and endurance testing of world class ultra runner, Rob Krar, this mens specific, body mapped runners vest is the ideal companion for those longer adventures and training days where there are no aid stations. Includes our patented 1. 8L Vapor hydration bladder, with a new design to reduce sloshing. Apparel like fit with a lightweight, breathable structure Compression system tightens the load against your back