Oil Filter Cover Metal Shim
This as an OEM quality replacement shim for the oil filter cover O-ring. This part was not installed in the final years of production of the two valve twins. In earlier models, there was a gap around the end of the tube that the oil filter fits inside of and the shim was needed to provide a solid seat for the O-ring and to prevent it from being pushed between the motor block and the filter tube. In later years, the end of the oil filter tube was widened to eliminate the gap. If you are retrofitting a paper gasket to your bike, also installing this shim is a good idea so that proper pressure on the O-ring is retained.