RioRand Cigarette Lighter Plug Digital Green LED Voltage Meter 12 V 24V+USB Car Charger 5V/2A For IPhone/IPad/IPod Size:75mm x 40mm Voltage measuring range: DC 8-40V ( DC12V/24V Universal ) Function 1: Car battery voltage monitoring,for 12V cars, SUV, 24V trucks, buses. Function 2: USB charger, for the charger of 0-2.1A cell phones, digital cameras, tablet computers and etc. Display: 3 bits, Green LED digital tube (if need RED LED,please check the item B00EZ031KC)