The Reizen Loud Ear 110dB Gain Personal Amplifier for the hearing impaired is a powerful personal amplifier with a built-in microphone for clear and loud delivery of voice and sound through the single mini earphone. This personal amplifier picks up sound at a distance up to 100 feet away. Handy built-in belt clip allows you to attach it to your belt or clothing. Includes 2 AAA batteries and single earphone. Additional earphones are available to use as spares or replacements. 90-Day Manufacturer's Warranty. SPECIFICATIONS Sensitivity: 110dB plus-or-minus 3dB per MW Frequency Range: 20Hz - 20KHz Estimated battery life: 48 hrs. Product dimensions (imperial): 2.5 inch H x 1.75 inch L x 0.75 inch W Product dimensions (metric): 63.50 mm H x 44.45 mm L x 19.05 mm W