I'm trying to source a new Crankshaft Sensor for my 98 model A6 2.8 Qt as I think I have a suspect one. The part number from Audi Aust is 078906433. When I search online I find some of the sensors for my car with this part number have the part number followed by a letter, sometimes A, or B or F. Eg, 078906433A.

Regardless of attached letters or not, all the sensors with that part number look identical

Does anyone know the relevance of these letters and whether they are critical to my situation?