This ideal solution is powered by DC 12V or 24V car cigaretter lighter charger.mini size of 1.2 X 1.58 x2.76 Inches. weight 30g.Easy to play, just insert the jack into a cigar socket then could display battery voltage immediately.Measuring range is DC 8V-30V.Constantly monitor battery voltage could extend and protect the battery for your car. No worrying that if the battery loss of electricity or can"t start the car any more. Note:Shells Group are always willing to work things out to meet your satisfaction. We value every customer and guarantee satisfaction. please feel free to contact us the first time you got questions about our products. please kindly aware of all Shells Patent item should with a special package,Shells Group will not responsible for any bad quality items that you buy from other sellers. Visit http://www.amazon.com/shops/shellsgroup for more reliable goods.