1Practical Brake Fluid Tester: Check the health status of your car brake fluid quickly, and remind you to change the brake fluid in time to make you more comfortable to drive. 2Simple Design: 5 LED indicators show the percentage of water in the brake fluid. The brake fluid tester pen is compact and portable, with a non-slip material and nickel-plated metal probe. 3Extensive Application: Support most of the vehicle with compatible for DOT3 DOT4 car brake fluid. This brake fluid tester is developed for both professional and amateur, widely applied in individual, repair factories and dealer workshops. 4Easy Operation: Install the 1*Aaa 1.5V battery(no included), press the button at the top, dip the probe into the brake fluid, and the test result will be indicated by LEDs in a few seconds. The brake fluid tester pen will automatically power off after about 15 seconds of inactivity. 5Note: If the green LED no longer lights up after pressing the button, replace the battery. After each use, clean the test probe with tap water.