Compatibility: Suitable for many standard CO2 cylinders with traditional trapezoidal thread TR21-4. After installation, you can use previous versions of CO2 cylinders, compatible with water aerators DUO, Art and Terra. High-quality materials: Our CO2 adapter is made of high-quality brass, rust-resistant, wear-resistant, and high-strength, offering higher safety, durability, and long service life. Easy to install: One end of the quick adapter connects to the Duo water carbonator, and the other end with TR21-4 thread connects to the 60L CO2 bottle. First, remove the pink part from the bottom of the soda machine by pressing the pin and pulling it out. For the new version of DUO and ART machines, a small portion of the bottle compartment shell may need to be removed to insert the bottle. Efficient and economical: With this adapter, you can continue using your original CO2 cylinder, avoiding the cost and inconvenience of replacing or exchanging CO2 cylinders. You can also use previous versions of CO2 cylinders. Note: Before purchasing, ensure your CO2 cylinder (including valve) is original and not a Quooker brand, as non-original cylinders may prevent the adapter from screwing in deeply enough to function properly. Color: Red Material: Metal Package Contents: 1 x CO2 Quick Adapter, 1 x Sealing Ring. Only the listed items are included; other products are not included. Note: Lighting reflections and differences in monitor settings may cause slight variations in color between the image and the actual item. Measurement allows an error of +/- 1-3 cm.