High quality shell, easy to stand alone or embed in the panel on the product. Black wire connect negative electrode, and red wire connect positive. Great accessory to display the battery capacity of your car. Type: Battery Capacity Tester Indicator Display Mode: Battery + Percentage Voltage: 12V Power Supply: Lead-acid Battery Size: 4.8cm x 2.9cm x 2.1cm/1.89" x 1.14" x 0.83" (Approx.) Battery Capacity Display Parameter: Battery Voltage >11.2V, 1 Grid Light Battery Voltage >12V, 2 Grids Light Battery Voltage >12.5V, 3 Grids Light Battery Voltage >13.3V, 4 Grids Light When battery voltage < 11.2V, the 4 grids all off, and it means you need to charge the battery right now. Notes: Due to the light and screen setting difference, the items color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Includes: 4 x 1 x Battery Capacity Tester Indicator