This item can be used for sound amplifier. When you see film / watch movie, enjoy the drama / watch the play, attend meeting, or have classes, the product can help you to hear the sound clearly and . While in forest, if you want to hear very slight sound, a . Features - ColorKhaki - Material: ABS - Size: 10x9x4cm - Output: &ge;120 - : &ge;30 - Distortion: f&lt;1000Hz<=10%,f&gt;1000Hz<=4% - Frequency Range: 250~3800 Hz - Input Noise: <=50 - Battery: 1 x (Included) - Working Voltage: .5V - Working : <=4mA - Super mini size and light weight, not easily to be seen. - Convenient for watching movie, enjoying the drama, attending meeting, or having class, it could help you hear the sound clearly and . - and sound amplifier. - Adjust volume to the minimum before wearing. - Increase volume gradually to avoid sudden increase in sound. Package list: 1 x K-86 3 x Earplug (different sizes) 2 x 1 x User manual