Bondo-Glass is a unique reinforced Body Filler containing short, interlocking fiberglass strands and fibers that make it twice as strong as regular Body Filler. The fiberglass in the filler eliminates the need for backing strips, Fiberglass Resin or cloth on small holes and rusted-out areas. It is capable of repairing small (dime size or smaller) rusted-out metal holes and shattered fiberglass body parts. It is compatible with all paint systems and also works great on boats!