Description: for wearers with severe hearing loss, the earhook provides a high level of amplification. Different size noise prevention earplug, adapt to the ear better. Adjustable ear hook style appearance, lightweight and compact. Convenient volume control, easy to use. Each item has been tested and checked in good condition before shipping. Specification: Material: ABS Plastic Input Noise: 30 dB Charger Type: US Plug Working Current: 4mA Working Voltage: DC3.7V Max Sound Output: 1274 dB Max Sound Gain: 48dB 5dB Harmonic Wave Distortion: 5% Frequency Response Range: 2503800Hz Size(LxWxH): Approx.4.35x2.0x1.3 cm/1.71x0.79x0.51 inch Package Includes: 1 Piece A-155 Hearing Aid 3 Pieces Earplugs (Different Sizes) 1 Piece Charger (US Plug) 1 Piece User Manual 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 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 do not use it for long time. Color might be slightly different due to the color calibration of each individual monitor. Please allow slightly measuring deviation due to manual measurement.