These do-nut style compression gaskets are used between various exhaust components in a typical Mazda exhaust system. These gaskets are designed to fit over the end of the exhaust tube that extends slightly beyond the edge of the mounting flange. Once seated in the recess area on the flange, these gaskets will compress when tightened, providing excellent sealing qualities. Mazda part number - LF45-40-305 This gasket is used on the following Miata applications: - Between the 1999-2005 Racing Beat header and the connecting pipe (stock or the Racing Beat Race pipe) This gasket has a larger ID than the factory gasket that would normally be used at this connection. - The inlet to the muffler on the 2007-2010+ MX-5 Miata.