J-B Weld Hi-Temp Silicone Gasket Maker Sealant Red, 85g, is a RTV (Room Temperature Vulcanized) Silicone gasketing material. Designed for use in mechanical assemblies where the existence of higher, continuous temperatures up to 287C (550F) or 343C (650F) intermittent might exist. Upon curing, which occurs when the product is exposed to the moisture in the 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.