Hi Dan: I suggest you remove the gasket and take it to a boat supply store to obtain an exact replacement. I have a MT 44 trawler 1979 with brass portholes and had no problem getting a replacement.. You might wish to buy enough to replace in the other port holes as required for the future. My original ones lasted 30 years before they got sticky. Store the unused ones in talc powder. Leonard Stern, INDIFFERENCE