Sika Sikaflex 221 Heavy Duty Adhesive Sealant is a multi-purpose 1-component polyurethane adhesive/sealant that bonds well to a wide variety of substrates like metals, metal primers and paint coatings (2-component systems), ceramic materials and plastics. It is suitable for making permanent elastic seals. Ceramic materials and plastics. It is ideally used for internal sealing and simple bonding applications. Seek manufacturer’s advice and perform tests on original substrates before using Sikaflex 221 on materials prone to stress cracking. This product is suitable for experienced professional users only. Test with actual substrates and conditions have to be performed to ensure adhesion and material compatibility.