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: Ensure correct wiring as per the included diagram. Use isolated power supply up to 20V or a common cathode DC-DC converter. Ensure 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/10A 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.