Features: Comfortable grip, strong impact resistance, fall prevention, dust prevention and waterproof. Brake fluid detection pen is based-on the change in conductivity to determine the moisture change brake-fluid. It shows clearly the extent of moisture contained by the light-emitting diode, high moisture content will lead to lower boiling-point, affect-braking performance. This auto-brake diagnostic testing tool can check the health-status of DOT3, DOT4, DOT5 car brake fluid. When it is-time to change the brake fluid, the LED light will go from green to yellow or red, reminds you to change the brake fluid, helps-you to avoid traffic accidents, provide you with a comfortable and safe driving. This check engine is small in size and easy to carry. Press the button and insert it, you can see the result of water content in your brake fluid. There are 5 LEDs indicating the water content in the brake fluid : 0 percent means-there is water content in brake fluid. 1 percent-means H2O1 percent, brake fluid is above standard. 2 percent-means H2O2 percent, still can use-it. 3 percent-means H2O3 percent, brake fluid should be changed. 4 percent-means H2O4 percent, brake fluid must be changed. This brake fluid-detector is widely used in most car, and it is suitable for detecting the moisture content in DOT3, DOT4, DOT5.1 brake fluid. This product has no-cable connector, it is convenient and easy to use. It can be used in personal-cars or repair shops. There is a small suggestion, after every testing, please clean the test-probe with dry cloth or paper. Specifications: Material:Nylon Size:Approx.13.8x1.8cm/5.43x0.7inch Color:Black Note: .Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. .Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thanks for your understandings. Package includes: 1x Brake Fluid Tester Pen