FWIW, bolts are NOT described by the size of the wrench used on them.

Rather, they're described by the diameter of the shaft, and typical German bolts requiring 10mm wrench have shaft diameter of 6mm and therefore are M6 bolts, i.e. 6mm bolts.

Now, if you were describing something from Japan, that same M6 bolt could require an 11mm wrench.

The same principle applies to inch-size bolts, too.

True 10mm bolts are almost lug bolt size. Yours, in fact, are 12mm, requiring 17mm wrench.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles