 When used with a pump, a lubricating gel is always used to help the pump maintain a vacuum, in the same way vacuum grease is used with a vacuum pump in scientific applications.The gel also makes it easier for the ring to slide off the pump, and later, to remove it from the penis.Some models include a protruding clitoral stimulator, designed to tickle the clitoris, vulva, or anus during sex (and during masturbation while the ring is used on a dildo).