|Smartballs are a variation of ben-wa balls, and are also promoted on the box copy as a trainer for pelvic floor muscles. The pair of balls are inserted vaginally. Each soft-surface ball has a metal ball inside that rolls around as you walk, giving a pleasant overall sensation of fullness and motion.
If you've ever had cheap hard plastic ben-wa balls, you will instantly recognize these as an improvement. The two balls are solid and unyielding, but unlike the hard plastic ones, they have a velvety, silky rubbery coating. Unlike the plastic ones, these muffle the sound from the metal balls inside, so you don't hear them clanging when you walk. The connector between the balls is firm but flexible. The pull-string allows easy removal, and is covered in water repellent rubber, which means it's NOT a germ-loving string and it's easy to clean.
You must move around to get the motion effect. They feel a little heavy. And after they are removed, there's a stimulating afterglow. A couple of minor irritations -- it first takes a while to get used to the coated string pointing through, making it feel like the balls are going to crown. The string is stiff and rubbery, and may pull skin or hairs. It's worth taking a moment to carefully position the string where it doesn't tug, and where it won't pull the balls out with the repetitive motion of walking.
Box copy quotes -- they provide a "targeted workout of the pelvic floor" and are recommended for postpartum exercises, to prevent incontinence, and for more sexual pleasure. Recommended by midwives. Made in Germany.
Overall impression -- Very nicely made. If they provide toning of pc muscles, that alone is worth it. As a sex toy, I find them more of a novelty, just enough to get, and keep, your attention.