The Magic Lube II Pool & Spa Silicone Lubricant sealant is formulated for use under the toughest conditions. It is an extremely durable, silicone base, synthetic compound that is non-melting and perfect for valves and other special applications that need the extra protection of silicone. It is USDA H-1 rated, environmentally safe, waterproof, and chemical resistant. Most sealants are petroleum based products. These products corrode rubber and therefore are not a good choice for pool and spa owners. This product has proven to be corrosion free on most materials, including rubber and is even strong enough for salt water!