RZ Hearing Aid Mini Ear Sound Amplifier Adjustable Ear Rechargeable Bluetooth Style USB Tone Hearing Aids Suitable for Deaf/Elderly about using 1.Adjust volume to the minimum before wearing.2.Choose an earplug of slightly bigger size to avoid whistler.3.Increase volume gradually to avoid sudden increase in sound.4.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. 5.Keep the ear plug clean6.Remove the battery if you don't use it for long time. 1.MaxSound Output: 1305 dB2.Sound Gain: > /=50 dB 3.Harmonic Wave Distortion:5(500Hz)4.FrequencyRange: 200-3800 Hz5.Input Noise:30 dBBattery: AG13 Button batteries (no included 1pcs)Working Voltage: dc1.5V Working Current:4mA Color: As the picture show Include package 1 Hearing Amplifier1 Shockproof Case2 hook1 Binaural matching headset line3 Earpiece (small, medium, large)1 Cleaning Brush1 Power Adapter1 Recharge plug1 User Manual About Paymet 1. We accept , , TT. All major credit cards are accepted through secure