This easy to use for SodaStream Cylinder Filling Adaptor will enable you to fill your own CO2 from your larger bulk cylinder into smaller for SodaStream cylinders. Disconnect the quick connector of the black adapter, and then tighten the black adapter to the for sodastream cylinder( must turn the knob on the top of the black adapter to the highest position,the whole process does not need to turn the adapter knob down to open the for sodastream cylinder,If the adjusting rod press down 6mm wide valve pin, this will close the valve and CO2 cannot enter).