Check the listing for details. Brake Fluid LED Diagnostic Tester Tool Quick Moisture Content Checker. Condition: New. Listed at 8.48 USD. Brake Fluid Diagnostic Tester Tool 5 LED lights display the percentage of moisture content in brake fluid Auto power off Requires 1 x LR03 AAA batteries (not included) Brake fluid detection pen is based on the change in conductivity to determine the moisture change in the brake fluid. Shows clearly the extent of moisture contained by the light-emitting diodes, high moisture content will lead to lower boiling point, affecting braking performance. Red indicates the brake fluid needs immediate replacement, green represents good condition, yellow indicates the state is acceptable but will need to be replaced soon. Note: Most manufacturers recommend that brake fluid is replaced every 3 years.Check which type of fluid (DOT 3,4 or 5) is recommended for your vehicle.Using the wrong type may lead to damage of the seals. 1, the green LED lights = water content in the brake fluid less than 1.5%2, the yellow LED lights = brake fluid water content 1.5% to 3%, can continue to use, test again six months later 3, the red LED lights = water content in the brake fluid greater than 3%, the brake fluid needs to be replaced 4, LED red flashing: battery replacement.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 lights to show that the battery is good, if the green light does not shine replace the battery Automatic shutdown.