Use this adapter, it's easy to refill your Soda cylinder with a big C02 tank, save time and money, get enough ! Small and exquisite design. Operating steps: 1. Screw the adapter onto the big CO2 gas bottle 2. Push the small CO2 clinder in the adapter and close the release valve. 3. Open the valve of big gas bottle slowly, about 15 to 20 sec, the small cylinder will be filled. 4. Close valve of the big gas bottle, then open release valve in adapter. 5. Pull the small CO2 cylinder out. Diameter=21.8mm Generally applicable to UK, Germany, France, , Japan, Korea, , Switzerland, Russia, Ukraine, South Africa, Sweden, Chile, Republic, Singapore, etc. CGA320 Diameter=20.8mm Generally applicable to USA, Canada, Brasil, Colombia, Philippines, etc. Colour:gold+copper+silver Material:Aluminum + copper type:A: TR21-3 to CGA320 Package Contents: 1 x CO2 Refill Adapter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.