I don't have a spare stem bolt i can measure. I tried measuring the bolt (all the same) on one of my bikes, but i come up with the smooth portion being under 40mm, then there is the threaded and the serrated ends, so i am fairly confident saying between the unexposed serrated and threaded ends, another 20mm would be present to make the difference. The short stems in Yamiya's pictures look too short and the longer stems in the pics look just right.