USB QC 3.0 Charger Digital Voltmeter with Scale Installation is very simple in the set there are all the necessary elements:Digital Voltmeter, Counter Nut, Connectors for connection Electrical connection is very simple, just connect the 6,3mm connectors to the device while maintaining the polarity of red [ ] , black [ - ] The meter can be used e.g. in cars, trucks, boats, yachts, motorcycles, ATVs and more Installation of Voltmeter: It is enough to drill a hole with a diameter of 29 mm, place the device in it, wind the nut, make an electrical connection. Working voltage: 5 - 15 V Power consumption: mA Backlight color: scale Attachment: in 29 mm hole Housing material: polyamide 6.6 Characteristics of USB: Working voltage: 12 V QC3.0 USB: 6V-3A; 9V-2A; 12V-1.5A; Rubber cover Application: Universal