Features and Benefits: Duraglas Fiberglass Filled Filler. Duraglas body filler is the original fiberglass reinforced automotive body repair filler. Formulated with short-strand fiberglass fibers, Duraglas provides ultimate strength and durability on rust-outs, holes, tears a; #1 Short-strand fiberglass filled body fillerReinforced for superior strength, Use with fiberglass cloth for large repairs, Rustproof. Waterproof.;