It is necessary to select the membrane according to the original number of the oil separator, since only the oil separator assembly is supplied in the original, we manufacture and sell the membrane separately!!! The diameter of the membrane is 57 mm. Alfa Romeo 1.9D 5607164 55197017 73500695 Fit for: 147 BZ/DS (2000-2010) 156 M.Y.2002 [...]