A, Best quality at low price B, Low noise amplifier C, Small and convenient amplifier D, ... Best selling in this year -WHY you choose it1.cheaper price,professional manufacture2.mini ITE style,invisible in either ear3.smaller ... fare7.amplify sound up to 40 feets,max sound level at 128 db8.CE ROHS certification -Technical SpecificsMaximum Saturation Sound PressureLevel ...