Genuine Honda 57.8mm x 2.4mm rubber o-ring. This o-ring is used under the oil filter cover on the CB/CL450K as well as the CB500T. If you haven't changed this o-ring before, odds are, it should be replaced since the centrifugal oil filter doesn't get serviced very often.
Note: There are 2 different o-rings under the oil filter cover. This is the smaller of the two. The other one is 63mm x 2mm, which is no longer available from Honda.
Honda Part Number: 91312-PC6-003
Very Similar to Honda Part: 91305-283-000 (58mm x 2.4mm)
Fits Honda:
CB450K - 1965-1974
CL450K Scrambler - 1968-1974
CB500T - 1975-1976
