Ben Wa balls

Ben Wa balls (also known as Chinese Meditation Balls) are small, marble-sized metal balls, usually hollow and containing a small weight that rolls around -- used for massage and meditation purposes as well as female masturbation. Some may also be solid, or contain clappers or chimes within.

Ben Wa balls are said to originate in Japan where they were called Rin No Tama and were either metal or ivory. Originally they were a single ball placed in the vagina used to enhance the act of coitus, but shortly evolved into multiple metal covered balls linked by either a chain or silk string for easy removal. Usage of Ben Wa balls create a subtle stimulation, not meant to bring the user to immediate orgasm but rather to tease. Women can "wear" Ben Wa balls all day, or use them while seated in a rocking chair, for pleasurable effect.

Ben Wa balls may also be used to simply increase the strength of the pelvic floor muscles, much as Kegel exercises are used today.