An antistatic wrist strap, ESD wrist strap, or ground bracelet is an antistatic device used to prevent electrostatic discharge (ESD) by safely grounding a person working on electronic equipment. It consists of a stretchy band of fabric with fine conductive fibers woven into it. The fibers are usually made of carbon or carbon-filled rubber, and the strap is bound with a stainless steel clasp or plate. An antistatic wrist strap prevents a shock hazard when working with low-voltage parts. Where higher voltages are present, extra resistance (0.75 megaohm per 250V) is added in the path to ground to protect the wearer from excessive currents; this typically takes the form of a 4 megohm resistor in the coiled cable ( or, more usually, a 2 megohm resistor at each end).