Features: Intelligent Charging:Dual USB ports totally for 4.2A and each for 2.1A.Will auto detect your devices and charge 2 devices at optimal speed in the meantime for maximum charging efficiency. Built In LED Voltmeter:Built in intelligent voltage monitor, with LED digital display, it real time shows you the accurate voltage status of car or motorcycle, more secure for driving. Waterproof and Temperature Resistance: The waterproof lid secures the USB port and leaves it able to work in splash conditions,made of ABS material,high and low temperature resistant. Overcharge Protection For Charging Safety:With overload, over-current and short circuit protection to ensure charging safety Wide Compatibility:This USB charger socket fits for DC 12-24V car, boat, marine, motorcycle,etc. Specification: Material: Environmentally friendly anti-flame retardant nylon material Input voltage: 12-24V Reverse protection: Yes Measurable voltage: 6-38V Output voltage: 5V Output current: 4.2A Working temperature: -20- 80 degree centigrade Installation range: suitable for installation of large-scale walking tools such as motorcycles, automobiles, ships, yachts, motor homes, buses, etc. Product Usage: 1.Support all mobile phones, tablets and car appliances (all models with working voltage 12-24V can be installed and used) 2.USB provides charging for car appliances, durable Wiring instructions: + connected to the positive pole of the power supply, - connected to the negative pole of the power supply. Package List: 1x USB Charger