Sikaflex-221 adheres well to a wide range 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 using Sikaflex-221 on materials subject to stress cracking. Preliminary tests must be carried out with original materials to avoid stress cracking. This product is suitable for experienced users only. To ensure adhesion and material compatibility, preliminary tests must be conducted with original materials under the respective conditions.