J-B Weld Black Silicone Sealant and Adhesive is a general purpose RTV (Room Temperature Vulcanized) Silicone, designed for sealing and bonding uneven surfaces. 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 and is great for many automotive accessories and household applications.