High Compatibility: Suitable for many standard CO2 cylinders with traditional trapezoidal thread TR21-4. After installation, you can now also use older versions of CO2 cylinders, compatible with DUO, Art, and Terra soda makers. High-Quality Material: Our CO2 adapter is made of high-quality brass, which is rust-proof, wear-resistant, and high-strength, providing greater safety, less susceptibility to damage, and a longer service life. Easy Installation: One end of the quick adapter connects to the Duo soda maker, and the other end (TR21-4) connects to a 60-liter CO2 cylinder. You must first remove the pink part from the bottom of the soda maker (press the pin to remove it). For the new versions of DUO and ART models, a small part of the bottle compartment housing needs to be cut to allow the cylinder to fit inside. Efficient and Economical: With this adapter, you can continue to use your existing CO2 cylinders, saving you the hassle and expense of replacing cylinders at the store. You can now also use older versions of CO2 cylinders. Please note: Before purchasing, please ensure that your CO2 cylinder (including the valve) is original (not Quooker brand), otherwise the quick CO2 adapter may not tighten sufficiently to work properly on the new soda maker. Color: Red Material: Metal Package Contents: 1 x CO2 Quick Adapter, 1 x Sealing Ring Only the above package contents are included, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to be slightly different from the real thing. The measurement allowed error is +/- 1-3 cm. When shopping, please pay attention to the size and specifications of the product to ensure it meets your needs.