3M 4000 UV is a fast cure medium strength sealant. 4000 UV is a one-part polyether sealant that cures to a firm, rubbery, water-tight seal. Excellent ultraviolet light (UV) resistance. Very low odor. Remains flexible. Bonds and seals metal, gelcoat, fiberglass, wood and plastic. Ultra violet resistance makes it ideal for bonding deck hardware, hatches, portholes, railings and navigation lights. Better choice (than 5200 polyurethane) for parts that may ever need removal or replacement, such as transducers. Use 4000 Fast Cure both above and below the waterline.