Multi functional OLED display voltage and current meter Includes button functions for easy data management and error correction related to component aging or temperature variations. Installation Guide: correct wiring as per the included diagram. Use isolated power supply up to 20V or a common cathode DC-DC converter. the black thin wire is insulated to prevent short circuits. Due to different batches, there may be differences in product appearance and printed text, which will not affect use Colour:Black Material:ABS Specification: 33V/3A Package Contents: 1 x OLED Multifunction Tester Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.