The conversion to LED indicators is really rather simple. However, the electrical load of the LED indicators is different from conventional indicators, and the frequency of the flashes is outside the permitted range. You can usually rely on a special LED flasher relay but that is not possible in all vehicles because the turn signal relay can be integrated with other components such as control parts or regulators. Therefore, there is this electrical drop resistor. Simply clamp between turn signal cables and turn signal connector in the wiring harness and the turn signal relay can operate at the usual flash rate. Note: the series resistor must be connected to each indicator. Requires so 4 items per vehicle.