When you buy Ben Wa balls make sure the joints are finished off neatly. Rough parts will irritate the vagina.
The two balls are connected with a piece of cord and have a separate cord for retrieval, which the girl leaves outside the vagina. Check the strength of the cord before you put them in and make sure the retrieval cord stays outside the vagina. Without a cord it can be quite a job to get them out.
Realise that you not only feel the movement of the balls clicking together, but you can also hear it. When you wear them when you have company over someone might ask where the sound is coming from…
To protect yourself against STD’s you should have your own toys. Don’t try or use the Ben Wa balls of a girlfriend, unless you cover them with a condom.