Sika Sikaflex-221 Non-Sag Polyurethane Sealant Aluminum Gray is a one component, moisture-curing polyurethane adhesive sealant that is used for creating a permanent elastic seal for substrates such as metals, wood, paint coatings, ceramics, and plastics. It is a non-corrosive, low odor, high quality sealant that is resistant to diluted acids, limewater, seawater, freshwater, weathering, and aging. Gray 300 mL Cartridge.