Industry standard, refillable co2 paintball cylinder
9oz Size (provides roughly 200-250 shots when full on most paintball guns)
NB: It is never a good idea to store your paintball gun gassed up - to avoid seals drying out, always remember to shoot out the remaining gas in your paintball gun after you have closed the tap valve on the cylinder (ensure the gun is unloaded and pointed in a safe direction when doing so).