A non-staining, non-shrinking, strip form sealant based on butyl rubber for sealing between normal building materials when the seal will be held in compression. It provides a waterproof, dustproof, flexible seal which can be painted and will accommodate a movement of approximately 20% in shear. It is used for sealing joints between cladding panels and for bedding and glazing, e.g. roof lights. It is available in various sizes in both circular & rectangular sections.