The Hyperseal Corporation has developed a singular unique caulk that utilizes recycled rubber from waste tires to form a non-toxic, non-carcinogenic caulk that cures to a solid flexible rubber. With such a high content of recycled rubber we have been able to go above and beyond what has been thought possible with acrylic-based caulks. The rubber makes the caulk extremely resistant to environmental damages such as hot & cold weather, and UV radiation. No other acrylic caulk can say that. It is tougher than toxic crack fillers and silcone based caulk and is safe for the environment.