1958-66 Ford Thunderbird, Carburetor Secondary Diaphragm – For Autolite 4100 4 Bbl Carburetor Late Style, (Hole center 40.8mm x 40.8mm)

This late style uses a plastic actuator arm. The early style uses a steel actuator arm. If you have the early style you will need the actuator arm (C5AZ-9853-A) to be able to use this late diaphragm.