Star brite® 98916 Ultimate Fiberglass Stain Remover, 16 oz. Gel formula 'sticks' where applied for maximum cling time and cleaning power. Removes yellowing and tough waterline stains. Completely covers stains to penetrate and dissolve them. Specifically formulated to remove the toughest stains, including rust, dried fish blood and leaf stains. Works on all fiberglass and painted surfaces; ideal for vertical surfaces.