5V / 4.2A Dual USB Car ChargerWith two USB charging ports and one output of 2.1A you can charge 2 devices at the same time at high speed. 10A fuseBuilt-in 10A fuse protects your devices from overheating, over-current, over-voltage, overload, under-voltage and short circuit. Wide applicationuniversally suitable for DC 12V-24V vehicles, boats and marine, motorcycle, truck, SUV, UTV etc. Easy installationThe hole diameter is 3 cm. It fits most vehicles control panels and rocker switch. "+" to positive pole, "-" to negative pole. A tight-fitting cap protects the USB ports when not in use. You can also connect it to an on/off switch and then turn off to save energy. Waterproof and Heat ResistantWith waterproof cover and is suitable for high and low temperature environments (-20C to 60C). Wide-ranging compatibility:Not only fits DC 12-24V automobiles, but also works perfectly on boats, ships, motorcycles, 4 wheelers, motor homes, etc. MultiProtect safety system:Device is certified by RoHS, CE and FCC. The surge protection, surge protection and advanced security features protect all your devices. Real-time monitoring voltage:Automatically monitors the vehicle battery and electrical system in real time and displays the voltage on the screen.< /p> How do I install it? 1. With a hole opener, drill a hole with a diameter of approx. 30mm. 2. Plug the USB charger into the opening. 3. Screw it tightly. How do i connect it? The terminals on the back are marked with "+" and "-" for positive and negative poles. Package Contents: 1 x dual port USB charger1 x wire with 10 A fuse