Compatibility: Fits many standard CO2 cylinders with conventional trapezoidal thread TR21-4. After installation, compatible with CO2 cylinders from previous versions, including 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 by pressing the pin to pull. For new version DUO and ART machines, a small section of the bottle compartment shell may need to be modified to allow bottle insertion. Efficient and economical: Use existing CO2 cylinders without replacement, reducing hassle 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 proper threading into the new soda machine. Color: Red Material: Metal Package Contents: 1 x CO2 Quick Adapter, 1 x Sealing Ring Only the above items included; other products not included. Note: Lighting and display differences may cause slight color variation between image and actual item. Measurement may vary by +/- 1-3 cm.