That would be the o-ring. The orange one in my kit is the same diameter as the shim. I've read so much about the $2000 o-ring that I had to ask. Will see what's on the bike now on replacement. Has anyone used the orange o-ring? Where I got the filter the guy definately wanted to help me out & went through several large books just to find the filter for a '78 air head. Did not show a listing for the white o-ring. My bike is low mile & I've done a couple oil changes this season due to its previous sitting, but got to do the filter. Dealer's in Louisville about 50 from where I'm at & just haven't made it yet. Plus I avoid the stealership when possible. Found filter local, may just have to look online.