Brake Fluid Tester Electronic Auto Car Pen Liquid Dot4 Dot3 Tool Brake Fluid Tester Note:Some orders with battery can not pass the Security examination. And many packages were returned as this reason. So we remove the battery,if you need the battery,you can buy one in your local area.Hope you can understand this! To Check Fluid Quality: Press the button for power on, green LED will light up. Insert the tester into reservoir for a second , then the results will be indicated correctly by LED's. Auto power off . Indications: Green: Battery OK, i.e.: No Water Contained in the Brake Fluid Yellow: Less than 1% of Water Content in Brake Fluid Yellow/Yellow: Approximately 2% of Water Content in Brake Fluid Yellow/Yellow/Red: Approximately 3% of Water Content in Brake Fluid; The Brake Fluid Should be Changed Yellow/Yellow/Red/Red: at least 4% of Water Content in Brake Fluid; Package: 1 piece Brake Fluid Tester If you have any questions,feel free to contact us!