Mounted Point, 1" x 3/4" Ball End A23 (Carded). Max RPM: 40,300. Shank mounted points and grinding wheels are made from durable, high-grade 60 grit aluminum oxide. Perfect for grinding, polishing or deburring ferrous metals or other hard surfaces. For use with 1/4" (6.35mm) chuck high-speed drills. Especially useful where larger wheels will not fit or where small abrasive wheels wear out too quickly.