In supple stretchy rubber, the smaller ring wraps around the base while the larger loops over the testicles, tugging subtly. The snug constriction can help keep over-stimulation under control and enhance orgasm when the moment finally comes (so to speak).
In 100% PVC the Duo cleans easily using warm soapy water or a good toy care fluid/foam.
* Smaller ring stretches from approximately 1.5" (3.8cm), large ring measures 1.9" (22.9cm)