You can have spare air tubes at the ready with the Air Tube Cylinders from Hatsan. These cylinders can be refilled while on the rifle or after they have been removed. They fit all Hatsan BT65 series Air Rifles and have a maximum fill pressure of 200 bar (3000 psi).FeaturesDetachable air cylindersMaximum fill pressure 200 bar (3000 psi)Easily screws in to all Hatsan BT65 series Air RiflesOption of refilling the air tube while on or detached from the air rifle