Ultra XP Carburetor 850 CFM 4150 Mechanical Secondaries Gasoline HolleyXtreme Performance Holley Ultra Xptm carburetors! Ultra Xp carbs are up to 38 percent lighter than our traditional race carbs, have fuel capacity that is 20 percent greater and 30 other new features! They're available in our all new Hard Core GrayTM hard coat anodized finish with BlackTM billet for improved corrosion protection. They're also available in natural tumble polished aluminum with your choice of BlackTM or RedTM metering blocks and base