Definition - What does Duotone Balls mean?
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.
Kinkly explains Duotone Balls
Duotone balls come in a string of up to four balls connected together. They are inserted into the vagina and worn to exercise the Kegel muscles and increase arousal.
They should not be used anally because they can easily become irretrievable (except by a doctor - yikes!).