Function: 1. SUITABLE MODELS: External thread Compatible with CO2 adapter Compatible with soda water is suitable Compatible with DUO, TERRA and Art soda machines. 2. THREAD AND USE: The thread of our CO2 adapter is TR21 4 external thread and can be inserted after removing the base of the 60L CO2 cylinder. There are different methods of use depending on different cylinders, easy to install. 3. POLISHED SURFACE AND GOOD SEALING: The soda CO2 adapter has a well-polished surface and good sealing so that CO2 does not leak. 4. EASY TO CARRY: The total weight of this CO2 coupler Compatible with soda machine is light and very easy to carry, you can take the coupler with you at any time. 5. MADE OF BRASS AND ALUMINUM ALLOY: The soda CO2 adapter is made of brass and aluminum alloy, corrosion resistant, durable and safe. Specification: Product Type: CO2 Adapter Material: Brass, aluminum alloy Thread: TR21 4-threaded Function: Connects TR21 4-threaded soda cylinders to DUO, TERRA and Art soda machines that use gas cylinders. With this adapter, you can continue to use traditional CO2 cylinders with screw valves. The adapter can be used with 60L aluminum CO2 cylinders with screw valves. Packing list: 1 x Coupler 2 x Washer Note: If the gas cylinder cannot be inserted into the machine when connecting a TR21 4-threaded soda bottle with a coupler, you must remove the baffle at the bottom of the machine so that the coupler and the gas cylinder can be inserted into the machine together.