This product is a Genuine BMW Brake Master Reservoir Cap without a warning switch. The part number is 34336770607. It is used as a replacement for the original brake master reservoir cap on BMW vehicles. This cap does not have a warning switch, which is responsible for triggering a warning light on the dashboard if the brake fluid level is low. This cap is designed to fit securely onto the brake master reservoir and help maintain the proper level of brake fluid in the system. It is a genuine BMW product, ensuring high quality and compatibility with your vehicle.