This professional tool is used to determine the quality of brake fluid in various vehicles, including cars. The design is compact and portable, shaped like a small pen with two metal probes at the end. These probes detect the fluid's quality, specifically the water content. Excess water is dangerous as it contributes to corrosion, increases overheating, and generally reduces brake effectiveness, which can lead to accidents. On the side is a power button, light indicators, and quality level markings for brake fluid. It is powered by AAA batteries.