Feature: 1. Accurate Measurement: The Brake Oil Detection Pen has powerful functions, simple operation, accurate measurement, and safe use. 2. Automatic Shutdown Function: The Auto Brake Diagnostic Testing Tool can detect all brake oil and has an automatic shutdown function. 3. Can Test DOT3/4/5 Brake Fluids: The Brake Fluid Tester has five LED indicators to display more accurate test results, and can test DOT3, DOT4, and DOT5 brake fluids. 4. LED Display: The Brake Fluid Inspection Pen determines the moisture change of the brake fluid based on the change in electrical conductivity. It clearly shows the level of moisture contained in the LED, and high moisture content can lead to a lower boiling point and affect braking performance. Red indicates that the brake fluid needs to be replaced immediately, green indicates that it is in good condition, and yellow indicates that it is acceptable, but will be replaced soon. 5. Suitable Battery: The Auto Brake Diagnostic Testing Tool requires a No. 7 AAA battery, and the battery cover is opened in the direction indicated by the arrow on the test pen. (Shipped without battery) Package include:1*Brake fluid test pen