The Heavy Duty Clay Bar is for cars that have never been clayed. The Heavy Clay Bar is for extremely rough and sticky paint finishes full of heavy industrial contamination, pollution, tree sap, and brake dust. Only use the Heavy Duty Clay Bar when no other clay bar makes the surface feel smooth as glass. If you need to use the Heavy Duty Clay Bar, chances are the surface has been neglected and needs to be polished to remove swirls, scratches, and wash marring that accompany years of daily driving and parking out in extremely polluted conditions. First wash the car, decontaminate it with the Black Heavy Duty Clay Bar, then polish to remove swirls & scratches before sealing the paintwork with synthetic sealant or natural carnauba wax. For the worst of the worst, bust out the big guns and take down the heaviest brake dust and contamination with the Heavy Duty Clay Bar and Clay Luber combo.