IZTOSS Brake Fluid Tester Automotive Tools Diagnostic Testing Tool Auto Brakes Calibrated for DOT3 DOT4 DOT5 with 5 LED Indicator Auto Brakes Calibrated For DOT3 DOT4 DOT5 LED light indicators show percentage of water in the brake fluid It determines the quality of brake fluid and measures moisture from 0%-4% Easy to use - simply power up, dip probes into brake fluid and read results,Only takes seconds to know the results Approved CE,RoHS.Includes protective cap. Staying safe and knowing that your car is in top condition is most important. Ideally, brake fluid should be checked regularly and changed every one to two years. As moisture seeps into the brake system through the brake hoses and seals the brake fluid will become contaminated and the danger of brake failure will increase. This pen-shaped brake fluid tester can easily help determine whether it&#039;s time for you to change your brake fluid. <span class="a-text-bold">Green:</span> None <span class="a-text-bold">Green/Yellow: </span>Less than 1% <span class="a-text-bold">Green /Yellow/Yellow:</span> Approx. 2% <span class="a-text-bold">Green/Yellow/Yellow/Red:</span> Approx. 3% (Time to change brake fluid.) <span class="a-text-bold">Green/Yellow/Yellow/Red/Red:</span> Approx. 4% (Change brake fluid immediately!) Turn on the brake fluid tester by pressing the button. A green light should light up. If the light does not come on, it may be time to change a battery. Unscrew the lid for the brake fluid reservoir, and take off the cap for the brake fluid tester. Dip the test probes into the brake fluid and the LED lights will indicate the percentage of water in the brake fluid. After testing, remember to screw the lid of the brake fluid reservoir back on tightly. Replace the battery if the green LED light no longer lights up after you press the button. Wash the test probe with tap water after every use. In case of skin contact with brake fluid, thoroughly wash the affected skin or clothing with water. Do not expose brake fluid to the atmosphere for a long time as it is highly Hygroscopic.