This is the connection you need if you would like to supply your own CO2 bottle or use our MiniInjector Kit for covering you wine with CO2. Remember you will not need to 'top off' the tank or buy a 'floating lid' for your fermenter if you use our kit or supply your own CO2 or nitrogen (N) bottle. The CO2 or N protects the wine from bad bacteria. The fitting size for the plastic reducer is 1/2 inch MPT to 1/4 inch NPT. The brass union is 1/4 inch MFL and 1/4 NPT.