3M Cubitron II coated 982C fiber disc uses ceramic as the abrasive material and has a diameter of 4 1/2 in. 3M incorporates this ceramic material into the fiber disc forming a grit of 36. 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 fiber disc can be run at a maximum speed of 13300.