Been a while since I'd changed plugs on a Beemer. So on my '08 RT I started with the top plugs. And damn, the 5/8 (16mm) socket was too "wide" to reach plugs. But behold, a second 5/8's in the box did...primary plugs out all good. Now for the down under ones, but the socket used to extract primary plugs will not fit. These two holes are smaller - why? I live in a town with a greater metro area population of over 350,000, but not one thin(ner) wall deep socket available to fit those secondary holes. Had to get the ole grinder out to have a "correct" size socket. I will never figure out "the BMW way".