e 3M™ Paint Preparation Pads to prepare panels before painting and keying alloy wheels and bumpers ready for refinishing. We’ve designed our pad to answer the call for a specialist pad for denibbing and alloy wheel and bumper keying. Get our specialist 3M™ Paint Preparation Pads to prepare panels before painting and keying alloy wheels and bumpers ready for refinishing. We’ve designed our pad for specialist denibbing and alloy wheel and bumper keying. Use the 2000 grade disc for denibbing of water-base coats while the vehicles are in the spray booth. Our 150mm discs are available as 20 discs per box.