Dynatron™ Dyna-Glass Short Strand can be used in conjunction with fibreglass tape, cloth or mat to repair and rebuild rusted-out metal or damaged fibreglass materials. This polyester filler is reinforced with short-strand fibreglass to create waterproof repairs that are twice the strength of ordinary body fillers. Dynatron™ Dyna-Glass polyester filler is reinforced with short-strand fiberglass to create waterproof repairs that are twice the strength of ordinary body fillers.