PFERD Coated Abrasive Disc, Standard, 4-1/2 in Diameter Disc, 7/8 in Center Hole, 16 Grit, Aluminum Oxide Abrasive, Fiber Backing, Arbor Attachment, Applicable Materials: Brass, Cast Iron, Copper, Zinc, Very Hard Aluminum Alloys, Plastics, Non-Hardened and Non-Tempered Steels, 13300 rpm Maximum