Product information:

Maximum sound output: 129±5 dB
Maximum sound gain: 55dB±5dB
Harmonic distortion: ≤5%
Frequency range: 450~3500 hz
Input noise: ≤30dB
Battery: 1 AA battery
Working voltage: dc1.5V
Working current: ≤4mA
Product size: 6.6 x 4.3 x 1.6cm
Packing size: 8.5 x 12 x 3.3cm
Net weight: 29 grams

Notes:
Turn the volume to minimum before use.
Choose larger headphones and avoid whistling.
Increase the volume gradually to avoid sudden increases in sound.
If you hear howling, please check whether the ears (silicone) are suitable, and if the plug size is too tight, please select the earplugs correctly and insert them to make sure that there is no air leakage.
Keep earplugs clean
If you do not use it for a long time, remove the battery.