90401-PR4-000 Washer (28Mm) - Overview. The 90401-PR4-000 Washer (28Mm) is a genuine OEM sealing washer used primarily within Honda marine engine sealing systems. This 28mm washer plays a critical role in preventing leaks by providing a secure seal at oil drain plugs and other similar system points. By ensuring proper load distribution and sealing function, it supports the integrity and reliable operation of Honda engines across marine and automotive applications including Accord, CR-V, Odyssey,