Permatex Optimum Black combines maximum oil resistance with maximum flexibility. Today, we see components changing and unlike materials meeting (plastic/steel, aluminum/steel, etc.), all with different rates of expansion and contraction. In addition, with technology advancing, regulations and requirements tightening, we see thinner metals, fewer fasteners, and wider spread bolt patterns. The strength and flexibility of Optimum Black handles the changes and added stresses that exist between today's lightweight, high performance, and premium component assemblies. Optimum Black is sensor safe, low odor, and non-corrosive with resistance to oil, shop fluids. It is one of the most advanced, maximum flex, maximum oil resistant RTV silicone gasket makers available.