Instructions: 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. 1. the green LED lights = water content in the brake fluid H2O <1.5%, brake fluid qualified 2. the yellow LED lights = brake fluid water content H2O = 1.5% to 3%, can continue to use, test again six months later 3. the red 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 4. LED red flashing: battery replacement 5. LED yellow: low moisture content, check again in six months 6. 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