3M 4200 White Fast Cure is a one-part polyurethane sealant that cures upon exposure to moisture, creating flexible, durable bonds. It adheres well to wood, fiberglass, gelcoat, select plastics, and metals, making it ideal for marine and general-purpose applications. This sealant is paintable and sandable, forming watertight, weather-resistant seals on joints and hardware both above and below the waterline. With approximately half the strength of 3M 5200, it allows for easier disassembly of parts without compromising reliable sealing performance.