3M 06560 4200 FAST CURE BLACK CAULKING. A one-part general purpose polyurethane that chemically reacts with moisture to deliver flexible bonds with good adhesion to wood, fiberglass, gelcoat, certain plastics and metals. Sandable. Forms watertight, weather-resistant seals on joints and boat hardware above or below the waterline. This product is approximately half the strength of 3M Marine Adhesive/Sealant 5200, which allows for disassembly of parts. Note: When very high strength or unremovable bonds are required, use 3M Marine Adhesive/Sealant 5200 or 3M Marine Adhesive/Sealant Fast Cure 5200. Not recommended for sealing wood decks because it may be permanently softened by certain teak cleaners or sealers.