HID headlight ballast Robust automotive design with rigorous testing for stability and vibration resistance, built to endure harsh environmental conditions in the vehicle. Compatibility: For BMW E66 models (20052008) with Adaptive Headlight Drive Control Unit and Cornering ballast. Key function: Assists headlights to light up quickly by delivering a higher voltage peak at switchon, improving initial illumination performance. OEM reference: OEM Part Number 7189312. Please verify your vehicle's part number before . Practical applications: Replacing a failed ballast in a BMW E66 20052008 with adaptive headlights to restore fast lightup and correct cornering functionality. Maintenance replacement to ensure reliable headlight performance on rough roads or in challenging driving conditions. Fleet or service use where dependable, rapid headlight activation is required across varying environments (urban, highway, rural).