3M Scotch-Brite MB-DC Silicon Carbide Deburring Disc - Medium Grade - 6 in Dia - 4000 Max RPM - 64419 [PRICE is per DISC]3M Scotch Brite MB DC deburring disc uses silicon carbide as the abrasive material and has a diameter of 6 in. Since this product is non woven, Grade is generally used to describe the abrasiveness; with the 64419 having a medium grade. All abrasive products that rotate or spin, such as the ones in this category, have a maximum speed at which you can run them. This 3M deburring disc can be run at a maximum speed of 4000.