My friend's a cosmetic surgeon and he says that they're called 'string implants' and they're made from a polypropylene string that grows inside the breasts even after the surgery.. They require multiple surgeries over time to stretch the skin enough to even begin to accommodate them. Even though they were banned in the U.S. a few years back, most MDs, including himself, wouldn't even consider the procedure as anything but unethical and a lawsuit waiting to happen. Even for the routine, low-risk cosmetic procedures like nose jobs, there's a high chance that most doctors won't take you if they suspect any signs of instability.