You can get them in many stores that sell herbal remedies and such, including some natural food stores. They stretch the ligaments and tendons in the hand and forearm, and I generally feel a little relaxation after using them. They've also improved my dexterity a bit.
Don't know what the generic name is. The instructions I got with my (translated from the Chinese by someone who didn't speak English well, congratulated me on the "purchase of your new iron balls."
So I can now honestly say I have balls of iron.