I bought a used '96 Audi A4 with 159K miles that had significant windshield sand pitting from extended highway driving in some sandy state somewhere. I used a variable-speed polisher at the recommended 1500rpm on one 4" diameter spot for 30 minutes and I couldn't remove even the smallest sand pits. Since the polishing compound is red, I suspect that the polish that comes with the kit is Iron(III), or ferric oxide, also known as jeweler's rouge, rather than the more commonly used cerium oxide which is white. Cerium oxide cuts quite a bit faster, but it is said that iron(III) oxide will give a superior finish. Anyway, if you have any kind of sand pitting, forget the sanding and polishing and get a new windshield.