Bondo-Glass is a unique reinforced filler containing short, interlocking fiberglass strands and fibers that make it twice as strong as regular body filler. Repairs small (dime size or smaller) rusted-out metal holes and shattered fiberglass body parts. PERFECT FOR MARINE USE! Eliminates the need for backing strips, fiberglass resin or cloth on small holes and rusted out areas. Sandable in only 20 minutes and compatible with all paint systems. Waterproof. Includes Red Cream Hardener.