SMARTCOAT™ 300 Non-Fibered Acrylic Mastic is a 100% acrylic elastomeric, water-based roof mastic intended to seal leaking seams, fasteners, penetrations and/or any splits, tears or deficiencies in the roof's surface prior to coating with SMARTCOAT 400/401 Acrylic coatings. This product is suitable for application to metal, asphalt, modified bitumen, concrete and most single-ply roofs. A high degree of rubber-like elasticity allows this product to accommodate wide swings in temperature and significant building movement. SMARTCOAT 300 Mastic is UV-stable; coating is not required.