Genuine OEM Audi Coolant Regulator, part number 4B3121113A. This critical component precisely controls the flow of coolant within the engine system, ensuring the engine reaches and maintains its optimal operating temperature. Weighing approximately 0.24 kg, this genuine OEM coolant regulator provides accurate temperature sensing and reliable valve operation, which is essential for engine efficiency, emissions control, and preventing overheating or undercooling.