Rigid polypropylene vent lengths with metal outer and dedicated male and female ends. Female end contains internal gasket and male ends can be field cut and chamfered to desired length. Centrotherm Eco Systems InnoFlue® Concentric Vent Length, 4 or 6 in ID x 6.8 in OD Dia, 38-1/2 in Length, Polypropylene, Gray/White, Domestic