Cometic C9888 Primary Seal/O-Ring Kit (AFM Series for Big Twin/XL Gasket) Cometic's proprietary am (aluminum fomite material) gaskets feature an aluminum core with a chemically blown, compounded nitrile synthetic rubber bonded to the outside Gaskets have resistance to temperatures of more than 2500 Degree Fahrenheit Have an 85% shape-recovering while maintaining strong torque retention - ideal gasket material for machined surfaces Does not require gasket sealer Kits include all gaskets, seals and O-rings required for both the inner and outer primary