From Chevrolet the DRL lights only come on during the day time, this harness allows the lights to stay on with the headlights which helps night time vision. It is also needed when upgrading your DRL to LED. We offer the harness by itself or you can add it to your order when purchasing LED bulbs. This harness is unique to ZL1 Camaros and will not work correctly on non-ZL1 Camaros or ZL1 conversions. Only one needed per car.