Aeroflow phenolic carburettor spacers improve air/fuel distribution and reduce the fuel temperature for a denser fuel mixture, reduce vapor lock, and add additional plenum volume to increase engine performance. They help with linkage clearance on aftermarket or custom throttle cable setups.
Phenolic spacers also block heat transfer better than any material.  The thermoset plastic provides a heat sink between an intake manifold and carburettor. With the harder material they will not warp heat cycles.
They are available in different heights in either open or ported designs to suit 4150 square bore manifolds with gaskets and mounting hardware included in all variations.