Ben Wa Balls are small, marble-sized metal balls, usually hollow and containing a small weight that rolls around—used for sexual stimulation (by insertion into the vagina or anus).Ben Wa balls may also be used to simply increase the strength of the pelvic floor muscles, much as the Taoist practice The Deer Exercise has been used for centuries, and the Kegel exercises are used today. Similar to Kegel exercises, Ben Wa balls and other shaped vaginal weights are recommended by gynecologists and obstetricians to increase vaginal elasticity and bladder control.