Unidentified carburettor diaphragm.
Possibly for Citroen BX16 ?
Full height: 41.5mm
Shaft diameter: 6mm
Length of area of shaft cut away to half-diameter: 25mm
Distance of start of cut away area from end: 3.6mm
Distance between any two of the three mounting-hole centres: 26mm
We do not know what car or carburettor this part is for, so please satisfy yourself that this is suitable for your application before ordring.