Proflow Aluminium Spacer, 1/2 inch. Open with Vacuum Port, Holley 4150 Carburettor Spacer, Each - PFECS320Part Number: PFECS320 Proflow carburettor spacers offer many advantages. They extend the length of the intake mixture column to improve air fuel distribution and reduce the fuel temperature inside the carb, resulting in a denser, more powerful fuel charge. Theyll also help with linkage clearance when using custom throttle setups. Theyre available in various thicknesses in both open and ported plenum designs. Stud kit and gaskets included.