Specifications:
Max Sound Output: 129dB ± 4dB
Max Sound Gain: 50dB ± 5dB
Harmonic Wave Distortion: 5%
Frequency Range: 450~3500 hz
Input Noise:30 Db
Battery: Lithium Battery
Working Voltage: DC 3.7V
Working Current: 3 mA
Measurement: 46*27*16mm
Net Weight:12g
Special Function Key: Rechargeable

Package Content:
1 x Hearing Aid
1 x Charger (110-240v)
4 x Earplugs
1 x User Instructional Brochure
1 x earphone

Note:
Adjust volume to the minimum before wearing.
Choose an earplug of slightly bigger size to avoid whistler.
Increase volume gradually to avoid sudden increase in sound.
If you hear a howling, check the ear (silica gel) is appropriate and whether the size of plug is tight, the appropriate choice of earplugs and plugged, make sure no air leakage.
Keep the ear plug clean
Remove the battery if you don't use it for long time.