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. Works great on boats! 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.