4-in-1 Design: This multifunctional panel is equipped with a 12V USB socket + a voltmeter with digital LED display + a 12V cigarette lighter + an LED rocker switch. Convenient to install and use. Also removable to replace other charging sockets or whatever fits. Waterproof Dual USB Charging Socket: This 12V USB charging socket features built-in dual USB charging ports, dual-port output: 5V/2.1A and 2.1A (total 4.2A). It automatically detects your devices and charges 2 devices simultaneously at optimal speed! Real-time LED Voltmeter: With a large digital voltmeter screen displaying voltages from 5 to 48V, you can monitor the battery status of your car or boat to check if the voltage is normal. On/Off LED Rocker Switch: Rocker-style design, easy to use. Long service life of up to 10,000 cycles. An additional cigarette lighter socket is portable for other devices in your vehicle. Overload Protection: Overheat, overcurrent, and overcharge protection; This dual USB charging socket is also