Polyfilla Professional X50 External Gap Sealant has been formulated with a unique polymer system for superior flexibility on exterior applications. Ideal for sealing areas and filling gaps that require painting as it remains flexible once cured to resist cracking, crumbling and falling out. Provides excellent adhesion to most building materials, including timber and synthetic weatherboards*, masonry, glass, fibre cement, ceramics, most metals, timber and plasterboard.