3M™ Milled Fiberglass Body Filler features short-strand chopped and milled fiberglass, making it an excellent reinforcement for repairing holes, cracks and tears in fiberglass as well as metal and SMC. Ideal for automotive and marine repair, this waterproof fiberglass body filler features a 2-part high-resin formula that delivers smooth spreading, excellent sag resistance and bond gapping.