This 1/2" thick CNC machined phenolic riser kit for the Holley 4150 and 4160 four barrel carb and will fit other models as well. It includes a 1/2" phenolic insulator, two gaskets, studs, nuts, and washers. Add a little performance to your machine the cheap way, and keep the heat away from the carburetor to solve the heat soak or carburetor boiling issues.