Standard EPDM gasket for 6 in through 12 in Dia InnoFlue® SW. Inserted into the female end of each part, the gaskets keep flue gases and condensates within the vent system. Centrotherm Eco Systems InnoFlue® Gasket, For Use With: InnoFlue® Polypropylene Vent Systems, 4 in Dia Nominal, EPDM, Gray, Domestic