It was 19mm-easier to get to from under the car.

Installation was pretty straightforward, other than having to swap the pulley over from the old unit to the new one (which uses an internal fan, rather than the external separate deal on the old unit)-needed air tools for that.

I soldered high grade ring terminals on the end of the old harness wires-looks great, now we'll see if it holds up (Thanks Steve).
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__________________
"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo