These are worn
inside the vagina. They are attached to a string like a tampon
and are two latex balls which roll around loosely inside the vagina
for stimulation and to aid muscle control.
One lady told me that
she likes to wear them when going out with her boyfriend as it turns
him on to know that they're in. It's a form of foreplay for
them. Some women just enjoy the feel of them. For others,
it has a turn-on factor prior to love-making with their partners.
Duo balls are also useful
for strengthening vaginal muscles after childbirth as these can
become slack and reduce sensitivity for the woman and enjoyment
for the male.