Features: Dual USB 3.1A output, can charge two devices at the same time quickly. With voltage, temperature and current meter tester. Built-in protective function for over charge, over current, over voltage and over heat. Fixed support helps stabilize the USB car charger. Multifunction design with 10A protection tube, perfect for travel use. Compact and light weight, it is very portable to carry. Descriptions: LED display the voltage, temperature and current alternately by each 10 seconds.  Apply to all USB charging mobile phones or other electronic products. This easily installed 5V, 3.1A output port holds your smart phone, GPS, MP3. Specifications: Output Interface: USB Input Voltage: DC 12-24V Output Voltage: DC 5V Output Current: 3.1A Voltage Measuring Range: 5-25V Current Measuring Range: 0.1A-3.1A Conversion Efficiency: 95% Temperature Measurement Range: -20 degrees to +80 degrees Material: plastic Size: 42mm x 78mm x 20mm Color: black Package included: 1 x 4-in-1 Car Charger Notes: 1.Due to the difference between different monitors,the picture may not reflect the actual color of the item. We guarantee the style is the same as shown in the pictures. 2.Due to the manual measurement and different measurement methods, please allow 1-3cm deviation.Thanks!