BTE machine, compact and light. Maximum saturation sound pressure level: ≤126dB±3dBMedium and high power hearing aids, suitable for people with moderate hearing impairment. Full range sound gain: 51dB±5dBConvenient volume control Total harmonic distortion:Convenient switch key 500Hz: ≤5%Color: Beige/Black/Silver 800Hz: ≤3%Configure dedicated charging base 1600Hz: ≤2%Frequency response range: 400Hz~5500HzEquivalent input noise level: ≤30dBBattery: Rechargeable lithium batteryWorking current: ≤3mAWorking voltage: DC 3.7 V