NortonĀ® Norzon Plus 66252843328 Grinding Wheel, Type 27 Depressed Center, Outside Diameter: 4-1/2 Inch, Thickness: 1/4 Inch, Arbor Hole / Thread Size: 7/8 Inch A.H., Grit: 20 (Coarse), Abrasive Type: Ceramic Alumina/Zirconia Alumina, Bond Type: Resin, Max Speed: 13580 Rpm, Mounting: Arbor, Product / Materials Abraded: Metal/Stainless Steel