Tuff Stuff, 4GMET, 4" X 1/4" X 5/8" Arbor Metal Grinding Wheel Depressed Center, Used To Grind Various Metals, , 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, Max RPM Rating 13,500.