Hi all. I am looking at the cam sprocket on my om603 engine. It is a 12 point bolt. The FSM says it is an M11 sized 12 point. I went to my tool box, pulled out my metric 12 point sockets send found that only a 13mm socket fits, though it is a little bit loose. So, are they different, M vs mm?

Trying to decide if I need another set of M sized sockets of if my mm ones are ok.

Thanks!

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1987 300TD named Klause
1987 300TD named Spouse
1987 300D named Seabiscuit
1980 300TD names Chloie (now sadly gone)

the 13mm is the head hex size, the M11 is the shank thread diameter.

a regular 10 mm hex head bolt is in real terms referred to as an M6 screw (further defined with the thread pitch).

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)