USMC Camelbak Thermobak 3 Litre (100 Oz) Hydration Pack. Desert Camo. Polyurethane Reservoir is slosh-free and collapses on itself 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