DESCRIPTIONS:Built in 400mAh Lithium battery,8 days working time after charge 1 timeBattery charging up to 2000timesDC 3.7V,loud and clear voiceMax sound gain up to 56dB±5dBLED light indicatorO-H-N swtich(On/Off switch,Low frequency adjustment)O~4 volume controlMain Unit Size 29*20*80mmDifferent size noise prevention earplug for you selectionUse the most splendid lithium battery power supply, provides the battery charger, no need to replace batteryCE CertificationStrict quality control,test by the hearing aid test machine of Fonix 7000 and Fonix 8000.SPECIFICATIONS:Color: RedMax Sound Output: 127±4 dBMax Sound Gain:48dB ± 5dBHarmonic Wave Distortion:  =5%Frequency Range: 450~3500hzInput Noise:  =32 dBBattery: Lithium BatteryWorking Voltage dc 3.7VWorking Current: =3mANet Weight : 200gWhat You Get:1 x Hearing Aid1 x Power Adapter 1 x Cable4 x Pair Earplugs (Different Size)1 x User Manual1 x Earphone