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 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 to the 60-liter CO2 bottle. Remove the pink part from the bottom of the soda machine by pressing the pin to release. For new version DUO and ART machines, slight modification may be required to the bottle compartment shell to allow proper insertion. Efficient and economical: Use existing CO2 cylinders without the need for 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 Note: Light reflection and display differences may cause slight color variation between the image and actual item. Measurement error allowance is +/- 1-3 cm.