DuraVent B-Vent Universal Adapters are used to connect DuraVent Type B-vent pipe to either another manufacturer's type B-Vent or a flexible chimney liner. Use the male adapter when converting another manufacturer's B-vent to the DuraVent B-Vent when the DuraVent will be on the top side of the vent pipe. Use the female adapter when converting the DuraVent type B-Vent to another manufacturer's type B-Vent when the DuraVent will be on the bottom side of the vent pipe.