This tester is designed to test the condition of your car relay to properly control the opening and closing of the relay. If the relay is abnormal, the red LED will light, and it's normal, the green LED will light. Car relay tester provides a convenient and intuitive diagnostic way, which is time-saving and economical. Auto diagnostic repair tool is portable, small and compact structure, you can test anywhere as you want. Car battery must be 12V battery, the voltage must be between 11-15V, the coil resistance is preferably at least 20 ohms. Specification: Material: PlasticandMetal. Color: Black Red. Size: 13x7x3cm Voltage: 12V. Note: There might be a bit color distortions due to different computer resolutions. There might be a slight errors due to different hand measurement. Package Included: 1 x Car Relay Tester. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.