It could be anything. How big are these cones? What are they made of? Obviously with wingnuts they are intended to be used by hand and be easily removable. Why does it take two cones to center an object?
There are two sets of cones, not to center an object, but to be centered upon an object temporarily to perform a task. Hence the wing nuts for easy removal. Here is another version of the same thing, notice the quarter as a reference to size. There are both larger and smaller sizes.
Nothing to do with a bow. The cones are adjustable to fit an object. Balance is a key word (sort of) in an object to be used with these, not the object it's used on. These objects, the object used with it and the object it is used on are not counterweights.
