ESR012 is a small 12V AC regulator that should be used in AC lighting systems on dirt bikes and some ATVs. These systems have a lighting output coming from the stator that feeds the headlight, and this regulator will prevent the voltage from going over 13V to keep your bulbs from blowing due to over voltage. Our ESR012 has only two connections: the BLACK wire goes to ground, and the YELLOW wire connects into the line between the lighting stator output and the headlight. Like all parts manufactured by ElectroSport, this part also comes with a full one year warranty.