Over-the-ear Hands-free Headset features an in-line volume control and MIC mute headset. Flexible ear hook fits either left or right ear. Noise-canceling microphone helps reduce background noise. Earphone has a 10mm drive unit, 55-3.7Kz frequency response, 32 OHM (positive/negative 15 percent) impedance, and sensitivity at 1KhZ: 98dB = +/- 4dB. Headset features a 2.5mm plug, 4' long cord and omnidirectional microphone.