Nathan's iconic featherweight hydration vest comes with a light and breathable perforated back panel to make your next 100-miler a breeze. Patented 3-way Propulsion Harness??? stabilizes side-to-side/up-down movement of bladder and other contents for a bounce-free ride. Highly breathable wall mesh shoulder straps, front bottle pocket and front zip smart phone- compatible pocket. External and internal mesh pockets. Wt: 14.6 oz. (w/bladder). 2L.