This 1/2" thick phenolic riser kit for the Pontiac Tri Powers with big Rochester 500 CFM outboard carbs with the small center carb. 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. This kit will do all three carburetors with the correct length for the studs. Why waste time fooling around with threaded rod and hardware store runs? Do it right the first time.