4 in 1 Multifunctional Panel: Features a 12V USB outlet, LED voltmeter, 12V cigarette lighter outlet, and LED rocker switch. Easily install or replace sockets as needed Dual USB Charger: Built-in waterproof dual USB ports (5V/2.1A each, total 4.2A) auto-detect and charge two devices simultaneously at optimal speed Real-Time LED Voltmeter: Large digital display shows 5-48V voltage, allowing you to monitor your vehicle's battery status in real time LED Rocker Switch: Easy to use rocker switch with a long lifespan of up to 10,000 cycles, plus an extra cigarette lighter socket for added convenience Safe Application: Built-in smart protect, ensuring safe and optimal charging for your devices, suitable for cars, boats, RVs, trucks ect, supporting various vehicle appliances