USMC Camelbak MULE 3L (100oz) Hydration System. Desert Digital Extra-wide, 1.75-inch/45mm opening can be filled with ice cubes for extra-cool hot weather hydrating HydroLock Valve provides positive shut off switch for anti-leak security Big Bite Silicone Valve releases more water when you need it Closed cell foam insulation keeps liquids cooler longer and doesnt absorb moisture or perspiration