Quoted from PinMonk:I mean AP went with hex cap tops on their Houdini bolts for the steampunk aesthetic, but at least the threading was still standard.
I don't know if the aesthetic was part of it, but the cool thing about American Pinball's leg bolts is you can take the same Allen wrench used for the backbox quick-lock and use it to tighten the leg bolts. It's really convenient.