Porter Cable's metal cleaning and polishing compounds are available in a range of five different grades for everything from aggressive heavy-duty cleaning (#1) to fine high-gloss polishing (#5). This is the #3 compound, the most gentle of the cleaning compounds used before polishing begins. The slightly gentler cut is needed when cleaning and finishing softer metals. Intended for use with a powered buffing wheel. Simply turn on your buffer, coat the wheel with compound, and you're ready to go.