J-B Weld Hi-Temp Red Silicone Gasket Maker & Sealant is an RTV (Room Temperature Vulcanized) silicone gasketing material, designed for use in mechanical assemblies where the existence of higher, continuous temperatures up to 550 F or 650 F intermittent might exist. Upon curing, which occurs when the product is exposed to the moisture in air, the silicone forms a tough, waterproof seal on most surfaces. It will not shrink or crack, resists weathering, is sensor safe and is great for many automotive applications. Set time 1 hour.