Quite funny to run into anal hook on Amazon.
Then, you discover the classic Ben Wa balls (阴道球), or just call it vaginal balls.
Ben Wa balls are traditionally 2 small marbles-sized metal balls you insert into the vagina. The point is to keep them there using your vaginal muscles, while you go about in your daily routine.
The glass ones are beautiful. And i was thinking, why not just buy marbles? They are cheap, abundant, and far more beautiful, and you can have more balls. You just need to get the right sized ones. 〈Mega Marbles - DRAGONFLY MARBLES NET〉 amazon. But, i realized that the glass ones lack weight. Imagine, when jogging, or on bus, or driving on a dirt road, you want it to jiggle and clash.
Modern ones, are made of plastic, stringed, and sometimes have vibrators builtin.
Kegel exercise means exercising your vagina muscles. Like, when you piss, you can control the flow by squeezing for pause. Better muscle tone down there means better sex; and that's the point of ben wa balls.