Remflex exhaust header gasket sets feature 100 percent flexible graphite construction that's effective up to 3,000 degrees F, far exceeding any vehicle's exhaust system temperature. They will rebound 30 percent when tightened, creating an optimum seal that eliminates the need for re-torquing. They're designed to crush up to 50 percent, filling uneven header flanges for maximum sealing and eliminating the potential for exhaust leaks. These gaskets are 1/8" thick and sold as a pair! Select which crate motor you are running between 602 & 604.