I purchased these to replace existing boat trailer/dust cover grommets of the same brand.  One of the original grommets had split apart and when I replaced it (and another one since there were two new ones in a package) I realized how poor of a condition the original grommets were in.  Replacement is easy, just pull the old ones out and the new ones 'snap' right in.  They must work well since I've owned this particular trailer about 10 years (purchased used) and the wheel bearings are in fine condition.