Feature: 1. COMPATIBLE MODELS: This SodaStream CO2 adapter connector is compatible with DUO, TERRA, and Art SodaStreamers. 2. INSTALLATION AND USE: The thread on our CO2 adapter is TR21 4-thread and can be inserted after removing the base of the 60L CO2 cylinder. There are different operating methods depending on different cylinders, making it easy to install. 3. POLISHED SURFACE & GOOD SEAL: The SodaStream CO2 adapter has a well-polished surface and a good seal to prevent CO2 leakage. 4. EASY TO CARRY: The total weight of this SodaStreamer CO2 connector is light and very easy to carry, so you can take it with you anytime. 5. MADE OF BRASS & ALUMINUM ALLOY: The SodaStream CO2 adapter is made of brass and aluminum alloy, making it corrosion-resistant, durable, and safe. Specification: Item Type: CO2 Adapter Material: Brass, Aluminum Alloy Thread: TR21 4-Thread Function: Connects TR21 4-threaded soda bottles to DUO, TERRA, and Art SodaStreamers that use gas cylinders. With this adapter, you can continue to use traditional screw valve CO2 cylinders. The adapter can be used with 60L aluminum CO2 cylinders with screw valves. Package List: 1 x Connector 2 x Washer Note: When connecting a TR21 4-threaded soda bottle with a joint, if it turns out that the gas bottle cannot be inserted into the machine, it is necessary to remove the baffle at the bottom of the machine so that the joint and gas bottle can be inserted into the machine together.