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: CO2 adapter made of high-quality brass, rust-proof, abrasion-resistant, and high strength for enhanced safety, durability, and long service life. Easy to install: One end connects to the Duo water carbonator, the other end with TR21-4 thread connects to the 60-liter CO2 bottle. Remove the pink part from the bottom of the soda machine (press the pin to release). For new version DUO and ART machines, minor modification of the bottle compartment shell may be required to allow bottle insertion. Efficient and economical: Use existing CO2 cylinders without the need to replace or exchange, reducing costs and inconvenience. 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 proper threading into the new soda machine. Color: Red Material: Metal Package Contents: 1 x CO2 Quick Adapter, 1 x sealing ring. Only the listed items are included. Note: Lighting and display differences may cause slight color variation between the image and actual item. Measurement may vary by +/- 1-3 cm.