Autolite 4100 Secondary Pump Diaphragm Kit    P/N APD201

This kit replaces both types originally fitted to the Autolite/Motorcraft 4100 series carburettor

Kit consists of Diaphragm, Gasket & Rocker Arm [OEM #: C5AZ-9853-A]
Having this rocker arm allows the diaphragm to replace both male and female OEM types. 

This is a vacuum diaphragm, not a fuel one, it opens the secondary throttle as the vaccum increases in the pimary venturis