3M Scotch Brite Gray 5 Inch Scuffing Discs Discs are used with a random orbital to condition finishes. Machine scuffing with these gray ultra-fine duty discs will produce faster results than hand scuffing. This scotch-Brite disc mates with a 5 inch hook and loop backing pad such as the 3M 77855. Common applications include conditioning marine, automotive and solid surface finishes.