1 307 329 068 1307329068 D1S D2S D2R Xenon HID Ballast headlight Ballast Control Unit The HID ballast is important because it helps to start the light and also allows current to flow through the entire bulb, thus keeping the light on. Recovery function - reliably replaces original components that have failed due to voltage surges in the electrical system Direct replacement, plug and play; no modifications required; no need to program or code the car. If you have any questions during use, please feel free to contact us directly and we will solve the problem for you within 24 hours.