Preferred Abrasives Firestorm FasTrim® Hi-Density Trimmable Flap Discs 80 Ceramic Grit 10921T-FFThese extra thick discs are made from Firestorm Ceramic material to provide a fast cut rate, and long life. Built in 5 8 11 threading screw directly onto the grinder without requiring locking nut. Every disc has a built in 5 8 11 thread ! Discs are Trimmable. When worn, the nylon backing plate can easily be trimmed back to expose more of the unused flaps. New low profile design allows the disc to fit inside the safety guard on the grinder. Grit: 80