Norton Abrasives BlueFire® Type 27 Depressed Center Wheel; Diameter: 4-1/2 Inch; Thickness: 1/4 Inch; Arbor Hole Size: 5/8-11; Abrasive Material: Zirconia Alumina/Aluminum Oxide; Grit: 24; Grade: Coarse; Tier: Better; Bonding Type: Fast Cut/INOX; Maximum Speed: 13580 RPM