Vitrified Mounted Point, 90 Grit, Fine Grade Aluminum Oxide, 3/8 in Dia./ SCREEN GRIT SIZE DESIGNATOR: 90 SPINDLE DIAMETER: 0.125 INCHES NOMINAL SPINDLE LENGTH: 1.500 INCHES NOMINAL ABRASIVE BOND GRADE DESIGNATION: O MEDIUM USAGE DESIGN: METALWORKING MAXIMUM SPEED RATING IN RPM: 61650.0 MOUNTING METHOD: SPINDLE WHEEL DIAMETER: 0.375 INCHES NOMINAL WHEEL STYLE: 123 A25 SPECIFICATION/STANDARD DATA: 80204-ANSI B74.2 AND B74.13 PROFESSIONAL/INDUSTRIAL ASSOCIATION STANDARD