Empty, refillable 14 oz. CO2 tank for use with the VetGun. Tank does not include CO2. It can be filled with CO2 at a gas/air supplier (Dick's Sporting Goods, propane, or welding shops, etc.) Cost to fill the tank is typically less than $10 and provides 300-400 shots before needing to be refilled again. The tank can be affixed to or removed from the VetGun as needed without losing CO2. Refillable CO2 tank affixes directly to VetGun without the need for an adapter.