eatures: 1. Low noise, low distortion. 2. Power supply: 2 X AG13 / LR44 batteries (included) 3. Behind the ear design, easy to use & carry. 4. Fit for right & left ears. Item type: Ear hearing aid Model: B-13 Maximum sound output: 130 5d B Sound gain: ≥ 50d B Total harmonic distortion: ≤ 5% Frequency range: 300 Hz ~ 40000 Hz Input noise: ≤ 30 d B Operating voltage: 1.5V Battery: 2 X AG13 / LR44 batteries Current: ≤ 4m A How to use: 1. Before you use this item, you have to turn the O-N switch to O (off) & turn the sound volume to minimum. 2. Then put this item on you ear, keep it tightly. 3. Next, turn this item on (O-N to N) adjust the volume until you hear clear sound. Package Included: 1 X Ear hearing aid 2 X LR44 battery 2 X Earplug 1 X English user manual Notes: 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 & whether the size of plug is tight, the appropriate choice of earplugs & plugged, make sure no air leakage. 5. Keep the ear plug clean. 6. Remove the battery if you don't use it for long time.