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 at a discount when purchasing LED bulbs. This harness is unique to ZL1 Camaros and may not work correctly on ZL1 conversions. Designed, manufactured and tested in the USA by Screaming Chicken. Only one needed per car.