Mr. Gasket MLS (multi-layered steel) header gaskets are designed for extreme cylinder pressures produced by high horsepower, high compression, turbo-charged, supercharged and nitrous equipped engines. MLS header gaskets are manufactured from three stainless steel layers that resist corrosion, will not burn through or push out, and maintain maximum fastener torque retention. Stress formed inner and outer layer embossments act like springs that rebound under exhaust flange clamp load, creating force to seal excessive exhaust pressure produced from cylinder heads. Required when installing headers, and HIGHLY recommended over the paper gaskets that are supplied with most headers. For all LS based engines. Sold per PAIR.