Viberating rings

Anyone have any experience with those viberating rings that go on the guy? Is there a particular one that is especially good? I've seen some that are kind of pricey, but not sure if they're worth the extra money. Getting my partner to orgasm even with extreme diligence and patience is like winning an Olympic gold medal so I'm always on the look out for new things to try.

Just my two cents worth, but, anything motorized just makes me numb. I've had OK luck with the Magic Wand, but it will numb me eventually. I guess me and vibrations just don't go together.