In reply to mike.gore:
Don't have mine with me, but I'm 183cm and went with the 6 step Yates big wall aiders which are 170-178cm (the lower number if you go with outdoorgearlabs review and the bigger one if you look at the Yates website).
Its worked out to be a pretty good length for me, and a pretty good set of aiders too. (Heavy, but comfortable and easy for use).
One could always cut off an extra step that wasn't wanted.