Easy to Use: Brake fluid tester pen with a simple control panel, the testing process is quick and efficient. With 0% to 2% of data, the backlight turns green (brake fluid is available). At 2% to 3%, the backlight turns yellow and the buzzer sounds slowly (brake fluid needs to be replaced). If the data is greater than 3%, the backlight turns red and the buzzer sounds. t fast (brake fluid. should be replaced immediately). Comfortable reading: the brake fluid tester pen has a high sensitivity probe + audible alarm, the results are displayed immediately, large display with three-color backlight, the results measurements are easy to read day and night. The results are visible after a few seconds of immersing the brake fluid tester pen in the fluid. The backlight reminder can quickly determine whether the brake fluid needs to be replaced. Automatic shutdown: The brake fluid tester is simple and convenient. It only takes a few seconds to check the quality of your car's brake fluid. The brake fluid tester is a must because it is small and easy to carry. The brake fluid tester also turns off automatically to save battery power when not used within 5 minutes. (Operates with 2 AAA/1.5V batteries, not included) Easy to carry: The durable and compact brake fluid test pen is made of premium plastic and is very sturdy and durable. Brake fluid tester: The case is well designed, compact and fits comfortably in the hand. You can take a brake fluid diagnostic tool when traveling and it does not take up much space. Wide range of applications: Car brake fluid tester is common in most vehicles. The Brake Fluid Diagnostic Test Tool checks the condition of DOT-3, DOT-4, DOT-5.1 and most synthetic brake fluids. This brake fluid tester is also ideal for testing the moisture content of brake fluids in trucks, motorcycles and other machines.