Collector and Header Muffler Gasket - 3 1/2 inch diameter - Embossed Stainless Steel - Multi-Layered Steel (MLS) exhaust and header collector gaskets are designed for extreme cylinder pressures produced by high horsepower-high compression turbocharged, supercharged, and nitrous oxide engines. Manufactured from three stainless steel layers, resists corrosion, will not burn through or push out and maintains 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 extreme exhaust pressure.