This is a pack of five replacement MP2 80/90 size exahust gaskets from Curtis Youngblood Enterprises. These gaskets are for use between the header and pipe on the MP2 80/90 pipe. Replace the gasket each time you remove the pipe from the header.
Also make sure to soak the gasket with thin gun oil when installing. The gasket will crush during first two flights so tighten the bolts holding the pipe to the header several times during the first two flights