SINSULL..supposedly, if one gets INTO one of those things while ummmm..not too excited...it is easier to maintain an erection after 'expanding' into the rings.(blood supply is trapped..etc) This allows (I gather) all sorts of play other than plain 'ol dull coitus..*grin*...(I have seen some with leashes attached...use your imagination).
There were also single rings and a couple of gadgets I'm not sure how they were supposed to work.

(Yeah...it was an interesting couple of years, but I only took my autoharp in once or twice....some weird customers were looking at it with appraising glances)(but the women I worked for were VERY bright, aware folks who didn't mind folk music at all)