Specifications:
Pocket Hearing aid
Max Sound Output: 129±4 dB
Max Sound Gain: 50dB ± 5dB
Harmonic Wave Distortion: ≤5%
Frequency Range: 450~3500 hz
Input Noise: ≤30 dB
Battery: 1 x AA battery (included)
Working Voltage: dc1.5V
Working Current: ≤4mA
Color: As the picture shows
Item Size: 7.0 x 3.0 x 2.7cm
Package Size: 12 x 8.5 x 3.3cm
Net Weight: 26g

Package included:
1 x F-22 Hearing aid
4 x Earplug (different sizes)
1 x AA battery
1 x User manual
1 x Box

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.