Another option is rings that have two or more vibes. The one I have looks like this when on.
This one can be worn a few other ways as well. The way above stimulates the wearer’s perineum and may also stimulate the balls too.
Worn this way it stimulates the balls and keeps the balls from sucking up during ejaculation.
This way it will stimulate not the only the balls but your partner’s perineum and or anus, in the doggie style position it may bump the clitoris as well.