The 5″ Wet 400 Grit Heavy Duty Resin Polishing Pad â 47379 is a stain finish or sealer finish disc. Hard wet resin polishing pads combine the benefits of resin and its ultra smooth finish with the longevity of diamonds. Wet resin discs last up to 4 times longer than dry discs when used correctly with water. If you plan on staining your concrete, now would be the correct place in the grinding/polishing process to do so. If you plan on continuing the polishing process, you would add the lithium densifier at this stage. If you plan on sealing your piece, stop the grinding process here.