J-B Weld Water Pump & Thermostat Housing Gasket Maker & Sealant is a specially designed RTV (Room Temperature Vulcanized) Silicone gasketing material for use in mechanical assemblies. Curing occurs with exposure to moisture in the air, forming a tough, waterproof, petroleum and weather resistant gasket and seal on most surfaces. This product is grey in color, will not shrink or crack, is sensor safe, has good temperature resistance up to 500º F intermittent and is great for many automotive applications.