I believe, if my math serves correctly... .7mm :google:
There is a long debate about whether or not there is a difference. From what I have read it seams that just that little bit of mm can cause a difference in balance at high speeds. But You can have them re-drilled to 5X115
Love mesh wheels. I'm looking at the same style for my car. Heres a few pics of the Nurburgring that Shifty mentioned above. Although, its made by TSW not BBS. BBS makes the more expensive CH-R
ACE offers the mesh style in 5x115, according to their pdf application file. I saw 20x8.5, 20x10 and 20x10.5. Not sure about their listed offsets although the literature on their website says they can offer up custom offsets.