3M LIGHTWEIGHT FILLER BONDO cures fast, shapes in minutes and is formulated as a durable material for repairing metal, steel, aluminum, fiberglass and concrete. 3M Bondo Lightweight Filler repairs dents, small holes, rust, scrapes and chips in metal, steel, aluminum, fiberglass and concrete. Our filler is a two-part product that comes with cream hardener.. With Bondo's Lightweight Filler you can complete quality repairs that are ready to sand in approximately 20 minutes at 75F. The fast-curing filler shapes in minutes, allowing for same day repairs. Bondo's Lightweight Filler comes ready to mix with its own cream hardener. Salmon color.