XT-491 is a high tear, high tensile strength, tin catalyzed silicone designed to be used when casting polyurethane foam, polyester and epoxy parts. XT-491 is useful for applications where a flexible rubber with increased chemical resistance is required. When catalyzed with one of our library life extending catalysts (see supplemental products) and stored correctly, a longer life of the cured mold should be expected. Its high tear strength, elongation and tensile strength make it an excellent choice for any mold making application. It is also resistant to inhibition by most common mold making substrates, eliminating the need to use mold sealers.