Bondo All-Purpose Putty is a professional strength, versatile filler for repairing interior and exterior surfaces around the home. This fast curing two-part filler allows you to make high-quality, long-lasting repairs to metal, masonry, concrete, wood, drywall and more. The non-shrinking filler features a thicker formulation that makes it ideal for repairing vertical surfaces. Light gray when mixed, helping blend with surfaces for consistent appearance. Fully paintable and stainable. Blue hardener.