SMARTCOAT™ 301 Mastic is a 100% acrylic elastomeric, water-based, fiber-fortified 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. While maintaining a high degree of elasticity, the addition of reinforcing fibers reinforces strength and delivers superior crack-bridging performance. SMARTCOAT 301 Mastic is UV-stable; coating is not required.