Compatibility: Fits standard CO2 cylinders with TR21-4 trapezoidal thread. Compatible with Sodastream DUO, ART, and TERRA water carbonators. High-quality material: Made of durable brass—rust-resistant, abrasion-resistant, and high-strength for enhanced safety and longevity. Easy to install: One end connects to the DUO carbonator; the other connects to a 60L CO2 cylinder with TR21-4 thread. To install, remove the pink base cap from the soda machine (press and pull the release pin). For newer DUO and ART models, minor modification to the bottle compartment housing may be required to accommodate the cylinder. Efficient and economical: Enables continued use of existing TR21-4 CO2 cylinders—reducing replacement costs and eliminating the need for proprietary cylinder exchanges. Important note: Ensure your CO2 cylinder and valve are original (not Quooker-branded), as non-compatible valves may prevent proper sealing or operation. Color: Red Material: Metal Package includes: 1 x CO2 Quick Adapter 1 x Sealing ring Note: Actual color may vary slightly due to screen settings and lighting. Dimensions are subject to a tolerance of ±1–3 cm.