All the photos show the ARB upside down.
ARB Dimensions
A – 980mm (centres)
B – 280mm (centres)
C – 27.5mm diameter
D – 240mm
E – 110mm
F – 340mm
Topic here – http://sprinter-source.com/forum/showthread.php?t=39835
Sprinter parts catalogue – http://www.ttcparts.com/uploadfiles/ttc%20mercedes%20sprinter%20catalogue%20final.pdf