14D511K Metal Oxide Varistor is a type of surge protection device that is designed to protect electronic equipment from transient voltage surges and spikes. It is made of a ceramic material that contains a zinc oxide powder, which provides the device with its nonlinear voltage-current characteristics. 14D511K Metal Oxide Varistor has a varistor voltage of 510 volts that begins to conduct electricity when the voltage across it reaches 510 volts.