Duotone balls are much like Ben Wa balls except that they are connected together by a cord and include a vibrating feature. The vibration may be electric and controlled via a remote, or it may be generated by the movement of small weights inside the balls. Duotone balls are encased in plastic or silicone. They are designed to help strengthen the pelvic floor muscles. Many women also derive pleasure simply from wearing them, or even using them during intercourse.
The term duotone balls is often used interchangeably with Ben Wa balls, but in the most traditional sense, Ben Wa balls are simply a set of weighted ball bearings.