This is a motor rod for Arri cameras. It looks like a lollipop and screws into the rosette where the handle would go. The mating side of the Hill 2-N-1 is made of nylon so it conforms the rosette and will not move. The name 2-N-1 means that it has two uses. The mount can be taken apart so you have a square to round rod that will slip into the square access hole on the Arri BL’s and the Arri 35-III handle.