B-LINEĀ® 4121878 Grinding Wheel, Type 27 Depressed Center, Outside Diameter: 4-1/2 Inch, Thickness: 1/8 Inch, Arbor Hole / Thread Size: 7/8 Inch A.H., Grade: R, Grit: 24, Abrasive Type: Aluminum Oxide, Max Speed: 13300 Rpm, Mounting: Arbor