Spacer Adapts Holley® 4150/4160 Series Carbs. Phenolic Material. 1/2" Height 4-Hole plenum Design. 1.75" diameter bores. Sold Individually.; Carburetor Spacer designed for Holley® 4150/4160 Carbs with 4-hole plenum design, 1/2" overall height and 1.750 inch Diameter Bores. Gaskets Not Included;.