if you look at the parts database for your variant ( in the top section of the B7 forum ) you'll see the OEM rims for your car plus the optional ones available to fit it, they are marked with the rim width/diameter and offset , by looking at this data you can ascertain what the factory Offset was/is on your car and then work from there, eg , many B7 came with 17"/18" rims with an ET43 offset, but other offset were also possible, so you can see the Et42 you are looking at are only 1mm further in, but at 19" tall , tyre width/rim width and rim diameter all cominto play aswell as the offset.