KoolFlex Mastic

KoolFlex Mastic is a professional-grade, high-solids, moisture-cure silicone mastic engineered for superior flexibility, adhesion, and long-term performance. Designed for critical repair and sealing applications, this 100% silicone formula is ideal for use on roofs, flashings, walls, masonry, and metal seams and fasteners, even in wet or underwater conditions. 

Formulated to deliver exceptional durability in extreme environments, Kool Flex Mastic becomes rain-safe in just 1 hour and remains permanently flexible without cracking or hardening. It bonds tenaciously to most common substrates including EPDM, concrete, metal, aged coatings, Kynar®-finished surfaces, and polyurethane foam without the need for primer in many cases.