"Cao Maru" means Round Face in Japanese, and that's what these designer stress balls are, basically - squishy round faces that stretch and squeeze as you take out your frustrations and relieve your stress.
There are 4 different faces in the Cao Maru lineup: Yuck, Relief, Joy and Pout. Which one you choose depends upon your mood. They weight 120 grams (almost 4 oz.) each, measure approximately 2.75 inches in diameter and two colors are available - natural (sort of off-white) and brown earth tone.
Polyurethane resin composition allows the heads to be distorted, pounded, crushed and so on; they spring right back to their original shape... your annoying co-worker's head, not so much. Take out your frustrations on a Cao Maru head instead, okay?
The Cao Maru stress balls were designed by Makiko Yoshida, a graduate (2003) of Tokyo University of Art and Design Faculty of Fine Arts. Yoshida's theory behind Cao Maru is that you should select a certain face based on your current mood; in effect capturing your feelings in the chosen face. By then physically morphing the face into a variety of different expressions, you can look at your feelings objectively and in the process relieve your stress.
Don't get too stressed by the price: 2,625 yen each (about $27.50) or $130 at Amazon.com for a set of 4 faces. (via Cataloger)
Editor's Update: The Cao Maru stress balls are now only about $30 on Amazon. Available in both black and white.