Miniature hearing aids, long-lasting charging in the charging compartment, comfortable to wear and clear soundThe main features of the product: 1. This is a super mini hearing aid that can hide perfectly in your ears. 2. Max Sound Output: 125dB 4dB 3. Sound Gain:30dB 4. Harmonic Wave Distortion: 10% 5. Frequency Range: 450~4000 hz 6. Equivalent Input Noise: 30 dB 7. Adjustable Volume Wheel1 4 volume 8. Battery: Built in High quality Lithium battery 9. Rechargeable battery duration max. 60 hoursShort Full charging time 4 hours (First charging up to 6 hours)