Fits #E8032 4" X 10" plastic opening port by Beckson.
Black rubber gasket. Typically used on the Capri 26, Catalina 250, Catalina 270, Catalina 310 and Catalina 320 where the opening port is installed in the fixed smoked plastic port in the head or galley. Check the dimensions of your port to confirm this is the port Catalina used on your boat.
Dimensions of port: