Universal for the vertial and horitontal air vent: The dimeter of the joint ball is 0.67 inches( 17mm). It is for the vertical and horizontal air vent. It cannot be used fo the circal air vent.
Easy to intall: It has the nut. You can screw the nut. The hook would lock the air vent and the clip will lock on it.
With support board; The phone couldnot fall down because the clip has two support boards on two sides.