3M 3-Radial Bristle Discs, 3/4" Diameter, Grit 220 - Red Great for cleaning and maintaining hard to reach areas on platinum, gold, silver, copper, pewter, and brass pieces. Embedded mineral abrasive is harder than most metals. Removes oxides without messy compounds. These discs do not generate the same amount of heat as rubber wheels do. Can be used individually, or stacked.