This is a new Accelerator Pump Diaphragm for Autolite/Motorcraft 2100 & 4100 model carburetors from 1958-1975.
Ford Motorcraft Autolite 2100 2 BBL Carburetor kit 289 302 351 390 427 Mustang
Ford Motorcraft & Autolite 2100 & 4100 Accelerator Pump Diaphram 2V & 4V 2 Pack
Ford Motorcraft Autolite 2100 2 BBL Carburetor kit 289 302 351 390 With Float
Ford Motorcraft Autolite 2100 4100 Idle Mixture Screw With Springs C1AE-9541C