Test the car brake fluid quality quickly to check whether its qualified. Five LED indicators show the test results more accurate. Calibrated for cars using DOT4 and DOT3 brake fluids; Only takes seconds to know the results, easy to use. CE and RoHS approved. Power : 1 x AAA/1.5V battery (not included) How to Use: 1. Turn on the brake fluid tester by pressing the button on top. A green light should light up. If the light does not come on, it may be time to change a battery 2. Unscrew the lid for the brake fluid reservoir, and take off the cap for the brake fluid tester 3. Dip the test probes into the brake fluid and the LED lights will indicate the percentage of water in the brake fluid 4. After testing, remember to screw the lid of the brake fluid reservoir back on tightly 5. The tester will automatically power off after 12 seconds of inactivity The LED lights will indicate the percentage of water in the brake fluid: Green: No water Green/Yellow: Less than 1% of water Green /Yellow/Yellow: Approx.2% of water Green/Yellow/Yellow/Red: Approx.3% (Brake fluid should be changed) Green/Yellow/Yellow/Red/Red: Approx.4% (Brake fluid must be changed urgently!)