The United Moulders (UM) lifejacket inflator uses a screw on cartridge and activates when it comes into contact with water. The cartridge mechanism has a compressed high powered spring which is held by a paper element. When the paper element dissolves it releases the spring which allows the firing mechanism to puncture the CO2 cylinder, the CO2 then travels through the manifold and inflates the lifejacket. The Automatic system is backed up by a manual override, which allows the user to pull the toggle and inflate the lifejacket. This is the 33g kit that includes the gas cylinder and the plastic screw on cartridge.