Feature:   1. Skin tone, blue, optional,  2. Air duct, which can be trimmed according to the size of the user's ears.  3. Four levels of volume adjustment  4.3 frequency mode switching  5. Regardless of left or right  6. The battery life is about 50 hours per charge    Specification:   Charging current: DC5V/50MA-1A  Battery: Lithium battery 60MAH  Size: 45*40*10MM  Weight: about 6.5g  Maximum sound output: 129±4db  Sound gain: 38±5db  Harmonic distortion: ≤5%  Frequency range: 400HZ-3800HZ  Voltage: D.C.3.7V    Tips:   1. Please turn down the volume to the minimum before wearing.  2. Choose slightly larger earplugs and avoid whistling.  3. Gradually increase the volume to avoid sudden increase in sound.  4. If you hear howling, please check whether your ears (silicone) are suitable and the size of the plug is tight,  Correct selection and insertion of earplugs can ensure air tightness.  5. Keep the earplugs clean.    Package Included:   1 x hearing aid  4 earplugs (different sizes)  1 x user manual  1 x storage box  1 x USB charging cable with charging head