Technical Data:

Peak OSPL90 (dB SPL): ≤116dB + 3dB
High Frequency Mean: 105dB ± 4dB
Peak Gain (dB): 30dB ± 5dB
Equivalent Input Noise: ≤30dB
Total Harmonic Distortion: ≤5%
Frequency Response Range: 250Hz ~ 3500Hz
Rated Power Supply Current Consumption: ≤2mA
Battery: AG10 Button battery (Included)
Color: As the picture shows

Package included:

1 x A-111 Digital Hearing aid
6 x Earplug (different sizes)
1x AG10 button cell battery
1 x Mini Brush
1 x User manual
1 x Box

About Whistle , you can do this 3 steps to remove it.

1. Choose a suitable earplug to make the product sealed in the ear canal
2. Low down the sound volume
3. When you put into battery , please be quick , to put the product into the ear

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.
Keep the ear plug clean
Remove the battery if you don't use it for long time.