●The quick adapter can connect not only the soda machine and the CO2 cylinders. You can also use this adapter to connect an old soda hose with a TR21-4 male thread to a new soda machine. Note: The quick adapter must be tightened, otherwise it cannot be used in a new soda machine. ●This CO2 adapter is made of strong brass and aluminium alloy with polished surface, tightly sealed, environmentally friendly, sturdy, high safety, rust-proof and durable for your long-term use. ●Quick adapter for 60L CO2 cylinder with TR21-4 push valve for connecting the soda machine, compatible with soda machine Duo type, Terra. (Other bottles of other brands are not recommended. Not compatible with manual CO2 bottles) ●With the quick adapter, you can use your original CO2 bottle to add your new lemonade