Carbon Dioxide Adapter TR21-4 to TR21-3 for Soda Water and Quooker Water Tanks: - Primarily used as a threaded adapter for soda water machine cylinders, it can also function as an air source switch. Made from high-quality materials, it features high hardness, tight threads, superior craftsmanship, stable performance, and easy installation and use.   If you wish to use the Sodasteam TR21-4 soda water cylinder instead of the Quooker Cube cylinder, this adapter can be used.   Thread specifications: TR21-4 female thread to TR12-3 male thread.   Notes: The product may be subject to ongoing updates. Due to different batches, the actual product may have minor differences or color variations, but these do not affect usage.   Color: As shown in the photo.   Material: Copper.   Package contents: 1 soda water carbon dioxide gas converter.