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 and cracks. Ideal for use on metal and fiberglass panels. #1 Short-strand fiberglass filled body filler Reinforced for superior strength Use with fiberglass cloth for large repairs Rustproof. Waterproof. *Cream Hardener Included