Also sometimes known as a Super Clamp.  There are Mafer people and there are Cardellini people.  The fact that the Mafer allows one to remove the stud and convert it to a clamp with a ⅝” receiver makes it more flexible in our opinion.  Also, aside from its lighting uses, if you install a round stud with a ¼” or ⅜” thread, the Mafer allows you to clamp almost any cinema accessory anywhere.  Proper pins are notched and the Mafer retains them with a spring loaded push lock, even if the screw knob is not tightened.