Fits 5" waste port. 5" lid / cap with ¼ turn thread (ID 110mm / 4.25" - overall OD 140mm / 5½"). In combination with a 5" tank collar/ring, used to seal water and waste tanks. Black. Polypropylene lid. 5" tank-mounted collar (ID 120mm / 4.25" - OD 155mm / 6")