Genuine OEM Audi Brake Master Cylinder, part number 4B3611021. This essential hydraulic component converts the mechanical force from the brake pedal into hydraulic pressure, which is then transmitted to the wheel calipers. It is typically mounted in the engine bay, connected directly to the brake pedal assembly. Constructed from durable cast metal, this unit weighs approximately 0.654 kg. A genuine OEM brake master cylinder guarantees the correct bore size, seal integrity, and pressure output for consistent, reliable, and safe braking performance.