These are absolutely the finest Carburetor Kits available anywhere at any price! We have combined every possible add-on feature and incorporated them into each kit to give you long and improved performance from your Holley Carburetor. Most of the features you would buy seperately are already included. Listed below are just some of the additional components. It Takes only five AED Carburetor Kits to cover virtually all Holley performance carburetors / which greatly reduces inventory and makes kit matching extremely easy.Pit Stop USA offers AED Holley 650-600 CFM Spread-Bore Vacuum Secondary Carburetor Rebuild Kit 4175 at low everyday prices. Be sure to check out all of our products from AED - Advanced Engine Design including AED Rebuild Kits.