Compatibility: Fits many standard CO2 cylinders with conventional trapezoidal thread TR21-4. After installation, you can also 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 connects to the 60-liter CO2 bottle. The pink part at the bottom of the soda machine must be removed (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 the bottle to fit. Efficient and economical: With this adapter, you can continue using your original CO2 cylinders, avoiding the hassle and cost of cylinder replacements. Please 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 above package content is included; other products are not included. Note: Light reflection and different displays may cause slight color variations between the item and the image. Measurement allows an error of +/- 1-3 cm. When shopping, please check the product size and dimensions to ensure it meets your needs. Detailed product information, including features and specifications, is provided in the title and description. We want you to be completely satisfied with your purchase. If you have any questions or concerns, please . We are here to help and will do our best to assist you. Thank you for choosing our product. We hope you enjoy it!