From the #1 Silicone Brand, Supreme Silicone Window & Door sealant is a premium, 100% silicone and100% waterproof sealant that can provide a reliable seal in weather-prone areas such as windows, doors, basements, roofs, sidewalks, siding, tuckpointing and attics. This sealant offers 40% more flexibility than Class 25 sealants and 7X stronger adhesion than Silicone 1 sealant. And, it offers 50% joint movement capability without cracking, shrinking, breaking down or washing away. This sealant has lifetime mold-free product protection to resist stain-causing mold and mildew growth. Backed by a lifetime guarantee.