This 1 inch tall phenolic thermoset plastic spacer insulates your carburetor against manifold heat keeping it cooler and helps prevent fuel percolation (also known as vapor lock) in hot weather. This can also allow for a denser fuel mixure to help increase performance in some applications, as well as provide additional plenum volume. 4-hole design is design for GM (General Motors) Quadrajet 4-barrel carbs and may also work with other spreadbore design carburetors. Gaskets, studs, washers and nuts are included.