How it works: In order for you to use it correctly, please follow our instructions: 1. Cool the soda machine cylinder in the freezer for 1 hour. 2. Screw the CGA320/W21.8 connector to a commercial CO2 gas cylinder. 3. Disconnect the quick connector of the black adapter, and then tighten the black adapter to the CO2 cylinder. Turn the knob on the top of the black adapter to the highest position. The entire process does not require turning the adapter knob down to open the CO2 cylinder. If the adjusting rod presses down the 6mm wide valve pin, this will close the valve and prevent CO2 from entering. 4. Connect the quick connector. 5. For most large cylinders: turn the cylinder upside down or lay it down. Some tanks do not have a dip tube (syphon tube) inside. 6. Carefully open the valve of the large gas bottle. The valve on the CO2 cylinder may stop the flow if opened too much or too quickly. Open the cylinder slowly until you hear the airflow. 7. After about 15–20 seconds, the cylinder is completely filled. 8. Close the valve of the large gas bottle. 9. Open the bleed screw to release residual gas. 10. Unscrew the CO2 cartridge. Please note: 1. If there is liquid CO2 inside the cylinder, turn the CO2 tank upside down if refilling fails when the tank is upright, as some tanks do not have a dip tube (syphon tube) inside. 2. The cylinder should be empty. Pre-cooled cartridges will fill more effectively. 3. Open the tank valve very slowly when filling to avoid engaging the 6mm wide protection valve on the soda machine bottle. 4. This adapter is not compatible with RPV valves (residual pressure valves). Refer to the product image. Some RPV valves can be removed using a hex wrench—please verify your valve type before ordering. If your tank has an RPV valve, select the "RPV pushing adapter" option when placing your order.