Pump diaphragm for the Weber DIR series carburetors.
These diaphragms now tend to suffer from age and the ravages of aggressive modern fuels which causes the "rubberized textile" material to harden and even crack, causing erratic running of the engine and fuel leaks.
Replacing the diaphragm is then the only sensible option.
Required quantity per carburettor: 1
This is item number 11 in the drawing.
Weber Part Number: 47407.131