This fuel log can telescope to fit either Holley carburetor models 4150 or 4500. The log is sealed with two O-rings which enables it to be shortened or extended. The -08AN carburetor fittings feature a 3/4 hex that extends away from the fuel bowl. There is a 3/8'' NPT female outlet at the rear of the fuel log to install a regulator or fuel pressure fitting. This fuel log is also capatible with alcohol race fuel.