Sikaflex-221 adheres well to a variety of substrates and is suitable for elastic, durable sealing. Suitable substrates include metals, primers and paints (two-component systems), ceramic materials, and plastics. Follow the manufacturer's recommendations before applying Sikaflex-221 to materials that are exposed to stress-induced cracking. Preliminary tests must be conducted with the original materials to avoid cracking due to stress. This product is intended for experienced users only. To ensure adhesion and material compatibility, preliminary tests must be carried out with the original materials under the respective conditions.