Sikaflex 221, white. Fast cure. Sikaflex-221 is a high-quality multi purpose non-sag 1-c polyurethane sealant ideal for use for Carvan and Motorhome repairs. Sikaflex-221 bonds well to a wide variety of substrates and is suitable for making permanent elastic seals of high adhesive strength. Suitable for use on many different materials including wood, metals, metal primers and paint coatings (2-c systems), ceramic materials and plastics.