We set out to find a possible simple fix to the leaking oil cap found on many E9x M3s. There are many reasons the leak occurs. From corroding magnesium valve covers to weak sealing caps. We wanted to create a simple inexpensive fix for the weak caps. Many people attempt to double up O rings, apply gasket sealant, or spend money on a new oil cap. Even though the factory oil caps are inexpensive, we have seen brand new oil caps that still are weak and leak. Our solution was to create a gasket O-Ring that was a single piece, replaces the factory OEM gasket O-Ring, provides thicker material to mate with the surface of the valve cover, and do so with cost in mind. $10.00 USD. About 60% cheaper than a new oil cap, you are able to replace your factory OEM O-Ring with an upgraded O-Ring that is made from Viton Florine Rubber and is 40% thicker than the factory O-Ring. Maybe not a fix for all oil leaks, but this has proven to be very affective with many leak issues associated with an oil leak from the cap. Installs in seconds and fits 100%with the factory OEM caps.