Gator Grit 25 Count 9" x 11" 320 Grit Very Fine Waterproof Sandpaper. The 320 grit very fine sandpaper is a waterproof sandpaper allowing you to sand automotive paints, urethane, lacquer, varnish, porcelain, acrylic enamel, metal primer, or clear coats. Sandpaper can also be used to rust stains from porcelain sinks and tubs. Sand with water to resist clogging and result will be an improved finish. To smooth surfaces sand in between coats. If using an orbital sander, the sandpaper can be cut into a 1/2 sheet, 1/3 sheet, or 1/4 sheet to fit the sander.