Surplus 3L bladder - army surplus - camelbak Specific style and availability vary, Used, recommend sanitation prior to Use Military Issued 3 L CamelBak Bladder, Military pre-qualified Burst tests included Fill to Max Capacity and soldier literally flops backwards onto the Bladder. Insulated Hose, On/Off Switch, Big Bite Valve and Large Fill Port makes Adding Ice and Cleaning a Breeze. Add these to any backpack you already have and never go thirsty or Sober again! Recommended for Water, works well with Rum, Vodka or cheap wine. Not recommended for Carbonated Drinks or you will have a new understanding of "Fountain Drinks" Air pressure Leak tested. The grey buttons at the Big Bite Valve and the connection to the Bladder Stem are to disconnect the Valve from the Hose and the Hose from the Bladder, for Cleaning repair replacement or Connecting to a Gas Mask Adapter