Sika Sikaflex 291 Fast Cure Adhesive Sealant 10.3oz(300ml) Cartridge - Black [90923]Sikaflex 291 Fast Cure Adhesive & Sealant 10. 3oz(300ml) Cartridge Black Sikaflex 291 is a 1 component, marine grade polyurethane elastomeric adhesive and sealant. Used by many boat builders, its fast cure time makes it ideal for applications where speed is important. Uses: General all purpose, marine adhesive and sealant, which may be used for light duty bonding. Sikaflex 291 has excellent adhesion to gelcoat, fiberglass, metal and wood that can be