Item features: Material: Aluminum alloy, Copper Color: Gold; Lilac silver Thread: TR21-4 Function: Connects CO2 cylinders with TR21-4 thread to DUO, TERRA, and ART soda machines with quick-connect cylinder system Properties: Fits common CO2 cylinders with standard trapezoidal TR21-4 thread, compatible with bottles up to 60 liters and 425g CO2. Made of durable, lightweight aluminum. Environmentally friendly, robust, safe, stainless, and long-lasting. 1. To install, remove the pink piece from the bottom of the Terra water dispenser by pressing the pins as shown in the included instructions and pulling the unit downward. For compatibility with DUO and ART models, a small section of the housing in the cylinder compartment may need to be trimmed to allow proper insertion of the cylinder. 2. Screw the quick adapter, with the flat seal inserted, securely onto the standard TR21-4 valve. Fits perfectly on 425g CO2 cylinders, including those from other brands such as Crystal 2.0, Penguin, Cool, and Aqvia. IMPORTANT: If the adapter cannot be screwed into the CO2 cylinder valve, the cylinder is not compatible with this adapter. 3. Insert the 425g cylinder into your Soda DUO, Art, or Terra machine and secure it by pulling down the quick-release lever and pressing the cylinder into the dispenser until it clicks into place. IMPORTANT: The hexagonal screw (safety valve) on the TR21-4 valve must face OUTWARD from the device, not sideways or inward. Why choose this adapter? Ideal solution if you have a blue CO2 cylinder but cannot refill it locally or prefer not to leave home. This upgraded quick adapter is specially designed for use with sparkling water makers and allows you to refill compatible blue CO2 cylinders. Simply refill your blue cylinder, attach the adapter, and use it with your Terra, Duo, or Art series Sodastream machines. Package includes: 1 x Quick Adapter