Lucas CAV DPS fuel injection pump diaphragm and piston commonly fitted to some Land Rover TD and Ford Transit vehicles.
The membrane can be bought separately if preferred. The symptoms of a split perished membrane is often a pressurised fuel tank and excessive smoke from the exhaust along with low power.
This is a quality aftermarket part, approx 41mm in overall diameter. If you prefer a genuine Delphi diaphragm please see HERE