Scrub Mask & Slate Cleaner is an effective, mild abrasive solution that deep cleans without scratching glass or most plastic surfaces. It removes product coatings, alkali residue buildup, pencil marks and grease pencil marks. Use the scrub on dive mask lenses and skirts, plastic slates and more. CAUTION: DO NOT USE ON PLASTIC LENSES. Don't just clean it---scrub it!