Brake pressure was transmitted by brake fluid, the pressure transmit will out of function once brake fluid include too water. In order to safe-driving, we must test water ratio scale in brake fluid regularly. The brake fluid tester help us do current maintenance, make sure we drive in safety condition.   Features: 3 LED lights show selected brake fluid types and 6 LED lights show percentages of water in the brake fluid.  Buzzing and red light double alarm system for more accurate testing and higher cost performance.  Universal fit for most vehicle. High precision to test DOT-3, DOT-4, DOT-5 brake fluid.  Made from premium quality material, this detector is resistant to oils and oxidation.  Hand-held size provide one hand operation experience.  This professional tool will help you save your time and money on testing and repairing your vehicle.   Specifications: Material: Plastics;  Power supplys: 9V(6F22) battery (included);  Package Size: 22 x 10.5 x 5.5cm / 8.66 x 4.13 x 2.17in;  Package Weight: 260g / 9.17ounce;   Operation Manual: 1. Install one 9V(6F22) battery at the back of tester.  2. After inserting the battery, press POWER button to turn on the tester, all LEDs lights turn on with buzzer sounding, which indicates the product self-test is successful.  3. Press SELECT button, it will locate DOT3 model automatically.  4. Each time you push the SELECT button, it will recycle from DOT3 to DOT4 to DOT5.1 with the indicator LEDs.  5. Immerse the probe into brake fluid and you will get different colors of LED lights, they indicate:   Green Light: indicates the brake fluid water content is below 1%;  The First Yellow Light: indicates the brake fluid water content is approximately 1.5%;  The Second Yellow Light: indicates the brake fluid water content is approximately 2.5%;  The First Red Light: indicates the brake fluid water content is approximately 3%;  The Second Red Light: indicates the brake fluid water content is more than 4%;  6. Press POWER button to turn off the tester.   Note: 1. After use, please clean the probe and avoid any retention of stains that might affect the test.  2. If in use for a long time, best to remove all batteries and store in a dry place at normal room temperature.   Package List: 1 x Brake Fluid Tester;  1 x User Manual;  1 * Battery