5 1/8" OPENING TO FIT MOST CARBURETORS INCLUDING EDELBROCK, HOLLEY, ROCHESTER, BARRY GRANT DEMON, ETC. FITS CHEVY, FORD, & MOPAR (CHRYSLER, DODGE, PLYMOUTH) CARBS. FITS MOST HOT RODS AND CLASSICS ENGINES INCLUDING GM (CHEVY, GMC, OLDS, CADILLAC, PONTIAC, BUICK, FORD, & MOPAR (CHRYSLER, DODGE, PLYMOUTH). ).