Here is the original thread.
http://forum.arcadecontrols.com/index.php?topic=63988.0To quote
Ok, some dimensions:
First, it's not the same diameter as a standard pushbutton hole. The threaded portion of the body is 1" long and .925" diameter, or made for a 15/16" hole. I think 1" would be fine.
The outside dims are 1.3" wide, by 1.96" tall. The actual button face is .938" wide by 1.588" tall.
They also have orientation pegs to keep them from spinning, so I guess they could be used with existing holes just by putting the smaller peg holes above and below the existing pushbutton hole and then tightening the nut down. I don't think it will go anywhere, and it should cover everything fine.