Not sure if they are factory but the #7's I pulled off had been there for awhile. I bought a pair of #8's off ebay to replace them. I did not notice the numbers on the old ones until I scraped a layer of crud off. I have seen pictures with the different numbers but can not find what they represent.

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If it ain't broke take it apart and find out why.

1983 300SD, 4 speed
1994 C280
1987 300TD wagon
1996 HD Road King

Ride in Peace Eric Peterson, Harley of Macon