How it works: 1. Cool the soda machine cylinder in the freezer for 1 hour. 2. Attach the CGA320/W21.8 connector to a commercial CO2 gas cylinder. 3. Disconnect the quick connector of the black adapter, then securely tighten the black adapter to the CO2 cylinder. Ensure the knob on top of the black adapter is in the highest position. Do not turn the adapter knob down to open the CO2 cylinder. Pressing the adjusting rod down onto the 6mm wide valve pin will close the valve and prevent CO2 from entering. 4. Reconnect the quick connector. 5. For larger cylinders, position the cylinder upside down or horizontally. Note that some main tanks do not have an internal dip tube (syphon tube). 6. Carefully open the valve on the large gas cylinder. The valve on the CO2 cylinder may restrict flow if opened too widely or too quickly. Open slowly until you hear gas flowing. 7. After approximately 15–20 seconds, the cylinder will be fully filled. 8. Close the valve on the large gas cylinder. 9. Open the bleed screw to release any remaining gas. 10. Unscrew and remove the CO2 cartridge. Important notes: 1. If liquid CO2 is present, invert the CO2 tank if refilling fails while upright, as some tanks lack an internal dip tube (syphon tube). 2. The cylinder should be empty before use. Pre-cooled cartridges fill more effectively. 3. Open the tank valve slowly when filling to avoid engaging the protection valve (6mm wide pin) on the soda machine bottle. 4. This adapter is not compatible with RPV valves (residual pressure valves). Refer to the provided image for identification. Some RPV valves can be removed using a hex wrench—verify your valve type before ordering. If your large tank has an RPV valve, select the "RPV pushing adapter" option when placing your order.