Mounted point, 3/4″ x 1/4″ a24 (carded). max rpm: 56,000. 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.