Compatibility: Fits many standard CO2 cylinders with conventional trapezoidal thread TR21-4. After installation, you can use CO2 cylinders from previous versions, compatible with water aerators DUO, Art and Terra. High-quality material: Our CO2 adapter is made of high-quality brass, rust-proof, abrasion-resistant, and high strength, offering higher safety, durability, and a 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 fits a 60-liter CO2 bottle. Remove the pink part from the bottom of the soda machine by pressing the pin to pull it out. For new version DUO and ART machines, a small section of the bottle compartment housing may need to be trimmed to allow the bottle to fit properly. Efficient and economical: With this adapter, you can continue using your original CO2 cylinders, avoiding the inconvenience and cost of cylinder replacements. Now you can also use CO2 cylinders from earlier versions. Note: Before purchasing, ensure your CO2 cylinder including the valve is original (not Quooker), otherwise the Quick CO2 adapter may not screw in far enough to work with the new soda machine. Color: Red Material: Metal Package Contents: 1 x CO2 Quick Adapter, 1 x Sealing Ring Only the items listed above are included; other products are not included. Note: Lighting reflections and display differences may cause slight variations in color between the image and the actual item. Measurement allows an error of +/- 1-3 cm.