The Sievert Self-Seal Butane & Propane Gas Cartridge is fitted with a threaded self sealing safety valve, ensuring safe and easy removal from the appliance and re-sealing automatically. Gas mixture consists of 35% Propane and 65% Butane for optimum performance. All cartridges comply with EN417 Regulations. Size 175gm. Tool Type: Butane/Propane. Fitting: Self-Sealing Valve.