TOPTUL JJDB0101 Brake Fluid Tester is a compact and easy-to-use diagnostic tool designed to quickly check the quality of DOT 4 brake fluid. Its five-LED system provides a clear indication of water contamination, helping mechanics identify when brake fluid requires replacement. With a 150 mm length and simple operation, it is suitable for routine brake-system maintenance across cars, trucks, motorcycles, and other vehicles.