We make these non-leakage cartridges for high-pressurized gas by ST52 seamless steel tube.We form the mouth and bottom of the cartridges with heated-roating-forming technology.As a home-used container of pressurized CO2 for beverage,we need these cartridges to meet the requirement for food,which should be non-rust,non-oil,non-particle inside other than be safe for pressurized gas.