Their function, according to Chinese medicine, is to stimulate the various acupuncture points on the hand.  This results in better circulation, the release of vital energy, thus creating harmony of mind and body.  

To exercise with the balls, you place them in your hand and stretch your five fingers in sequence to cause the balls to rotate either clockwise of counter-clockwise.  In doing so, all the joints of the hand are always in motion.  As you progress you can move on to larger balls or use 3 to 4 balls.    

These balls are vintage from the late 80's - early 90's.  They are like new and have only been displayed/stored.  The balls are 1.75" in diameter and decorated with red, blue, and gold cloisonne enamel.  One ball has the image of a dragon; the other a phoenix.  Comes with case and instructions.  Case has very light fraying.    Please refer to pictures.  Shipped to U.S. only.