Compatibility: Fits many standard CO2 cylinders with conventional trapezoidal thread TR21-4. After installation, compatible with CO2 cylinders from previous versions, including those used with water aerators DUO, Art, and Terra. High-quality material: Made of high-quality brass, rust-proof, abrasion-resistant, and high strength for increased safety, durability, and long service life. Easy to install: One end connects to the Duo water carbonator, the other end with TR21-4 thread to the 60-liter CO2 bottle. Remove the pink part from the bottom of the soda machine by pressing the pin to pull. For new version DUO and ART machines, minor modification may be required to the bottle compartment shell to allow bottle insertion. Efficient and economical: Use your original CO2 cylinders without the need to exchange them, saving time and cost. Compatible with previous version CO2 cylinders. Note: Before purchasing, ensure your CO2 cylinder and valve are original (not Quooker), as non-original parts may prevent the adapter from screwing in properly. Color: Red Material: Metal Package Contents: 1 x CO2 Quick Adapter, 1 x Sealing Ring Note: Light reflection and display differences may cause slight color variation between image and actual item. Measurement error allowed is +/- 1-3 cm.