Specification: Brake fluid detection pen is based on the change in conductivity to determine the moisture change brake fluid. It shows clearly the extent of moisture contained by the light-emitting diode, high moisture content will lead to lower boiling point, affect braking performance. Red indicates the brake fluid needs immediate replacement, green represents good condition, yellow indicates the state is acceptable but soon replaced.   The green LED lights = water content in the brake fluid H2O 3%, can not continue to use the brake fluid needs to be replaced. Red LED: change brake fluid. LED red flashing: battery replacement. LED yellow: low moisture content, check again in six months. LED green: brake fluid lines / cell row.   Features: Five LED indicators show the test results more accurate. Testing DOT 3, DOT4, DOT5 brake fluid. Press the switch to turn on the power, the green LED light that represents the battery properly, the green light does not shine on behalf to replace the battery Automatic shutdown.   Technical Parameters: Green: battery ok, that is, brake fluid does not contain water. Green / yellow: brake oil in water content of less than 1%, better brake fluid performance, ease of use. Green / yellow / yellow: brake oil in water content of about 2%, brake fluid can continue to use. Green / yellow / yellow / red: brake oil in water content of about 3%, the proposed replacement of brake fluid. Green / yellow / yellow / red / red: brake oil in water content of at least 4%, the brake fluid must be replaced immediately responsible for very dangerous. Item Name: Brake Fluid Tester Power: 1 x LR03 AAA 1.5V Battery (Not Included) Length: 15.5cm(Approx.) Notes: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Includes: 1 x Brake Fluid Tester