Five gears for accurate measurement, different color lights, easier to distinguish and remember: the first light is on, indicating that there is no water in the brake fluid, so you can use it with confidence; the first two lights are on, indicating thatthe water content in the brake fluid is 1%, and the performance of the brake fluid OK, rest assured to use; the first three lights are on, indicating that the water content in the brake fluid is 2%, and the performance of the brake fluid is good,but it needs to be checked frequently; the first four lights are on, indicating that the water content in the brake fluid is 3%, and the performance of the brake fluid is poor. It is recommended to replace the brake fluid; five lights are on, indicatingthat the water content in the brake fluid is at least 4%, and the brake fluid needs to be replaced immediately. Reminder: After each test, wipe off the liquid part of the test point with a dry cloth or paper towel. Instructions: 1. Open the probe protective cover on the front of the test pen, press the button lightly, and the green light at the bottom of the five indicator lights on the pen will light up. 2. Insert the metal probe in front of the test pen with the green light on into the car oil pot in parallel, and both probes must be in contact with the oil surface. 3. Identify the condition of the brake fluid according to the color of the light on the top of the detection pen. 4. After the test is completed, after 10 seconds, all the lights on the test pen will go out, and the test pen will enter the power saving mode. One battery can be used for a long time, and the test pen basically does not need to consume much power. Alwayskeep it in the car, and always know your brakes Oil quality, convenient and fast. Delivery Quantity: 1pc Package Contents: Only the above package content, other products are not included. no battery provided Size: 15.5*1.8cm (Reminder: The size is measured manually, please allow 1-2 cm measurement error) Colour: Black (Due to different monitors and lighting effects, the actual color of the item may be slightly different from the color shown on the picture.)