Features Professional brake fluid detection pen: specially designed for simple inspection of brake fluid quality. Insert the tester into the water tank for a period of time, and then the indicator light will display the result correctly. 5 LEDs indicate the result: 5 LEDs indicate the percentage of water in the brake fluid. A water content of 1% to 2% means that the fluid is still usable, and 3% to 4% means that you must change to a new fluid to drive safely. If the percentage is greater than 3%, replace the brake fluid. Easy to use: press the button above to turn on the tester. The green LED starts to light up. Keep the test rod in the brake fluid for a period of time. Then the LED displays the test result, and the tester automatically shuts down after 12 seconds. Professional tool: The tester can be used as a digital brake fluid tester, suitable for determining the quality of brake fluid. Specially developed for professional use in car repair and maintenance shops. Portable size: compact, light and portable, it is a good helper for your travel. The LED light will indicate the percentage of water in the brake fluid Green: Power on Green/yellow: less than 1% Green/yellow/yellow: Approximately. 2% Green/yellow/yellow/red: Approximately. 3% (Time to replace brake fluid.) Green/Yellow/Yellow/Red/Red: Approximately. 4% (replace the brake fluid immediately ) Brake Tester 5 LED display results: 5 LEDs indicate the percentage of water in the brake fluid. A water content of 1% to 2% means that the liquid is still usable, and 3% to 4% means that you need to replace it with a new liquid to keep it safe. If the percentage is greater than 3%, replace the brake fluid. Battery powered: Powered by 1.5V AAA battery (not included). Warning: The green light goes out when you press the button, please replace the battery immediately. Clean the test needle with tap water after each use. If your skin or clothes come into contact with brake fluid, please wash the affected area with water. Do not expose the brake fluid to the air for a long time, because it will strongly absorb moisture.