I'd be curious to know how they shorten them. I was first thinking cutting and welding, which may not be sound, but on the website, the cranks look so clean, my guess is starting with a long crank and drilling and tapping a pedal hole at a shorter length, then cutting off the end. (Starting with long crank, so original pedal hole is well away from new hole, so new hole has sufficient metal all the way around it.) Note, this will be a problem with a hollow arm crank, or one that is a U section (away from the original pedal hole) and not rectangular section.