Buyer has choice of rubber or stainless hat lines and brass or alum. nozzle bodies. RBS will set up for your specific application at no extra charge. Fits 6-71 thru 14-71 superchargers with a 13.250" on center bolt pattern. Butterflies dia. is 3.69" and are available in red, blue or black. Racer must pick what fuel and with or without fins on the injector from the drop down menu.