RidevaDemocritusBased on this, "The quarter-inch mounting point is compatible with most standard tripods and other photography and videography accessories.", I'd say 1/4-20 stud up top and same size hole on the bottom.
NoseyI read that as well, but without pictures I just didn't know for sure. I mean, the most likely thing would be quarter-twenty but it's Monoprice, so I only believe 86% of the copy.