Genuine OEM Volkswagen Tandem Master Cylinder, part number 3D0611021A. This component is a critical part of the hydraulic braking system, responsible for converting the force applied to the brake pedal into hydraulic pressure that actuates the brakes. It is typically located in the engine bay, connected to the brake booster and brake lines. This part weighs approximately 0.65 kg. Genuine OEM master cylinders are precisely engineered for correct fluid displacement and consistent braking performance.