Star Brite® Gel FSR Xtreme Fiberglass Stain Remover 16 oz. A powerful, no-sanding formula designed to remove stubborn stains caused by rust, tannins, and brackish water. Ideal for use on boats, RVs, and fiberglass surfaces, this gel-based cleaner clings to vertical areas for deep penetration and effective stain removal. Simply apply, wait, and rinse for immediate results. Safe for fiberglass, gelcoat, and painted surfaces, it works on decks, hatches, showers, and sink basins.