These Magnum discs feature the longest-lasting aluminum oxide abrasive bonded on durable, reinforced plastic that ensures extended life and outlast paper discs . With their brass centers, these flexible discs can be changed instantly. Great for finishing carvings! Use discs with a snap on/off disc mandrel, item 15097. Maximum speed 30,000 rpm. 7/8" Diameter. 25 pieces each in fine (320 grit), medium (220 grit), coarse (150 grit).