Gator Grit 3 Pack 4-1/2" x 7/8" 80 Grit Medium Fiber Sanding Disc. The fiber disc is designed to be used on angle grinders with a backer pad and used for aggressive sanding of metal, fiberglass and painted surfaces. The sanding disc is to be used with a 4-1/2" backer pad and fits 4-1/2" angle grinder