J-b weld ultimate grey gasket maker and sealant is an RTV (room temperature vulcanized) silicone gasketing material designed for use in mechanical assemblies where higher torque or closely spaced bolt profiles can lead to higher loads and cause gasket and sealing failures for average silicones. Upon curing, which occurs when the product is exposed to the moisture in air, the silicone forms a tough, waterproof, gasket and seal on most surfaces. It will not shrink or crack, resists oil and petroleum products, resists weathering, is sensor safe, has good temperature resistance up to 500 degree Fahrenheit intermittent and is great for many automotive applications.