4-1/2" x 1/4" x 7/8" Arbor, Fast Cut Metal Depressed Center Wheel, Double Reinforced With Industrial Grit & Glue For Increased Life & Durability, Superior Friability Allows Wheel To Break Down Quickly Consistently Exposing New Grain For Increased Sharpness & Longer Life, For Low Angle & Vertical Grinding, Bulk.