Simple Brake Fluid Tester ToolDigital measuring provide quick and easy way to test the presence of water in the brake fluid, specially developed for car users & garage mechanics.Check the quality of brake fluid in car only takes seconds. Make it easier to operate for beginner. Its a must-have car tool for your car owners. Press the button for power on, the green LED light that represents the battery properly, the green light does not shine on behalf to replace the battery.Insert the tester into reservoir for a second , then the results will be indicated correctly by LEDs. Auto power off . Brake fluid detection pen is based on the change in conductivity to determine the moisture change brake fluidIt 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. Five LED indicators show the test results more accurateCheck the health status of DOT3, DOT4 car brake fluid, it will be safer for your driving.Power supply by AAA batteries (not included). This tester pen with a pen clip for easy clip on your shirt and convenient to carry around.Designed for checking the quality of brake fluide quality simply.