Unique, extra strength stain protector specifically formulated for grout. Tuff Duck is a penetrating sealer which leaves the natural finish unaffected. It delivers the maximum protection for natural stones. Formulated with advanced, water-based fluoropolymers. Tuff Duck stone sealer by Rocklinite Labs is specially formulated to protect against the toughest oil and water based stains. The sealer is compatible with marble, granite, limestone, slate, terrazzo, travertine, sandstone and other porous stone surfaces.