This hard plastic tube is meant to reside in the place of a balsa filter, for those who smoke 9mm Filtered pipes but don't use filters. It lessens the size of the draft hole from 9mm to 6mm. Because the tube is tapered, one side is able to fit 6mm balsa filters if that size of filter is your preference! These are not needed in order to smoke Savinelli filtered pipes without a filter; however, they are an option for those smokers who prefer the draft hole to be a smaller size. In addition, a 6mm adapter can be purchased and fit inside this 9mm adapter, to restrict the airflow to that of a 3mm unfiltered pipe.