Fill your pcpair rifle on the go with this lightweight Carbon Fibre Hoop Wrapped Cylinder - 6.8l , 300BAR with air restraint valve for Air Rifles. These specialized tanks for refilling high-pressure airguns are incredibly convenient because they don't rely on electricity and fill the gun's tank very fast. This tank is very lightweight and takes up little space, but holds a lot more air than smaller cylinders. You should always ensure your cylinder is filled with filtered, dried air that won't put any moisture into your gun that could cause rusting problems.