Sika Sikaflex 291 Polyurethane Marine Sealant Black is a one component, moisture curing, elastic adhesive and sealant that is used for bonding boat building materials such as fiberglass, wood, metal, and gel coat. It is fast curing, stable, high solid, NSF approved for potable water, USDA approved for food contact, and used above or below water. It is resistant to salt water, fresh water, diluted acids, limewater, and caustic solutions. It can be applied by painting, squeezing, or brushing methods.