These look like a bracelet made of copper wire and have awesome torque. They come out of the box inside a ring-shaped neodymium permanent field magnet, from which they must never be separated, and their magnetic field is so intense that you must never, ever, overload them or you will demagnetize the field magnet and turn the whole thing into a piece of $1000+ scrap metal. On the project for which we were using them, this happened all too frequently when the driving transistors failed and connected them across the 100V, 10A supply with no current limit. About once a week we’d hear a BANG! from the servo section followed by five minutes of loud and colorful curses.