Type 27 Raised Hub. Made for a wide range of grinding, shaping and cutting jobs in home workshops, farms, and machine shops. Aluminum oxide is recommended for all types of ferrous metals. Wheel dimensions are diameter x thickness x arbor.Wheel Diameter (in.) 4 1/2 Wheel Thickness (in.) 1/4 Arbor Size (in.) 7/8 Max. RPM 12,000 Wheels (qty.) 1 Wheel Type Type 27 Recommended Use Masonry