Ben Wa balls, also known as orgasm balls, rin-no-tama, Venus balls or Geisha balls (“vagina ball”, “internal-use ball”), are small, marble-sized balls, usually hollow and containing a small weight, that roll around and are used for sexual stimulation by insertion into the vagina. Available in a variety of forms, the balls may be solid or contain clappers or chimes within. Other, larger versions made of plastic encasing lesser balls are called Duotone balls. They are used by inserting them into the vagina and using the pubococcygeus muscles to hold them in, stimulating movement and/or vibration. Ben Wa balls should not be confused with anal kegel exercisers and prostate stimulators for men: Ben Wa balls sometimes have a retrieval string or attachment of some sort, but they do not have an adequately flared base for safe anal play.