Not a shim. It's a very thin stainless steel sleeve that you press on to replace the seal wear area. See your local bearing supply house. Instructions for installation will come with the sleeve. Part # is SS99175.
OM, do you think they were talking about a thin shim to have the seal not go in so far so it would sit in a different spot than the worn groove? Instead of putting on a new wear sleeve like a person should. Just a thought!!!
May be but for $20 to get the right sleeve I'm not going to try to cobble things up with a shim.