Camelbak Ambush Hydration Pack, Black, Made of Cordura, 16x10x6, Mil Spec Crux Short Reservoir Included, Reservoir Holds 3 Liters 1722001000 Perfect for shorter missions" the Ambush optimizes the area on a user's back with a wider platform" shorter torso length and reduced stack height. With external access to the 3L" 100oz Mil Spec Crux Reservoir that provides 25% more water per sip" the Ambush is our largest hydration pack that includes external fill.