This series Bluefire R884P Type 27 trimmable flap sanding disc measures 4 1/2 inches x 5/8"-11, has 80 grit zirconia alumina abrasive grain, and a maximum RPM of 13,300. For use with a right angle grinder, this blue disc has a fibreglass and resin backing and features enhanced grain shape, durability, and versatility.