This is another one of those small sealing washers to insure that all of the cooling air is flowing over the engine and not out the open holes! order all of the other sealing washers at the same time like the spark plugs and the oil pressure switch grommet.
Oil drain plug copper washer for Boxster. Measures 18x24mm. Oil drain plugs use soft metals such as aluminum or copper to create a good seal. In order to prevent an oil drip after oil drain, it is necessary to replace the gasket. For oil drain plug gaskets, see aluminum and copper gaskets.