Unique 1/2" spacers are precision machined on state-of-the-art millworking centers, and can be used individualy or stacked without the use of gaskets Thin layers of choice laminated hardwood, bonded together with resin, form a natural thermal barrier Top-quality hardwood has a sheet of phenolic resin- impregnated paper bonded to both sides Can be easily modified to your particular manifold for optimum performance Gaskets are not included *Not legal for sale or use on pollution-controlled vehicles