A Wartenberg Wheel (also called a pinwheel or neurowheel) is a popular BDSM toy. It was originally designed by Dr Robert Wartenberg as a medical device to test nerve reactions as it glided across the skin. A Wartenberg Wheel is generally made of stainless steel with a handle of approximately seven inches in length. The wheel, which has evenly spaced radiating sharp pins, rotates freely around as it is rolled across the flesh and of course the pins stick in; the harder the wheel is pressed, the more pain is caused, so it can be used for anything from gentle teasing to torture. Disposable plastic versions are available.
Wartenberg Wheels have also been adapted to work with TENS units for use in electrical play. A single wheel (with an insulating handle) can be connected to one electrode on a TENS unit, this requires that a second electrode be attached to the sub to create the curcuit. An alternate design uses two pin wheels joined together, each wheel acts as an electrode, the current flowing from one to the other through the skin of the sub. The effect of the current heightens the sensation of the pins on the body.