A cavity inside another cavity, here is a hollow 120-toothbrush
ball with a hollow 60-toothbrush ball within it. There are 30 in
each of the six colors, making up the 180 toothbrushes in total.
The two rotate independently, making for a light and open feeling.
At just the right relative position, the colors and symmetry axes of the
two balls line up.
This sculpture was commissioned by Dr. Donald Kahn, D.D.S. for his office waiting room in Farmingdale, NY.