4. Made by high-quality Material, oxidation matte treatment makes it lighter, more beautiful, and stronger. 2. New integrated design and improved internal sealing structure avoid the use of any seal glue and are and more . 3. With 8mm male quick disconnect, easy to connect the female head, standard size, combined tightly, no air leakage. 1. This adapter applies to all soda water machines with TR21-4 interface, used for connecting external carbon dioxide cylinder/tank. 5. Comes with a small wrench for easier installation and disassembly.