Compatibility: Fits many standard CO2 cylinders with conventional trapezoidal thread TR21-4. After installation, compatible with CO2 cylinders from previous versions, suitable for water aerators DUO, Art and Terra. High-quality material: CO2 adapter made of high-quality brass, rust-proof, abrasion-resistant, high strength, provides higher safety, durable, and long service life. Easy to install: One end of the quick adapter 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 pull). For new version DUO and ART machines, a small part of the bottle compartment shell must be cut to allow bottle insertion. Efficient and economical: Use your original CO2 cylinders, avoiding the need to exchange cylinders and reducing replacement costs. Compatible with previous version CO2 cylinders. Note: Before purchasing, ensure your CO2 cylinder including the valve is original (not Quooker), otherwise the quick CO2 adapter may not screw in sufficiently to function with the new soda machine. Color: Red Material: Metal Package Contents: 1 x CO2 Quick Adapter, 1 x Sealing Ring Only the above package content is included; other products are not included. Note: Light reflection and different displays may cause slight color variation between the image and the actual item. Measurement allows an error of +/- 1-3 cm.