Califone 3066AV Deluxe Multimedia Stereo Wired Over-the-head Headset, 3.5mm Plug Designed for language learning in todays classrooms. Its noise reducing earcups and microphone help filter out external distractions to keep students on task. Its also ideal for VoIP applications, gaming, and for use in computer labs and other multimedia applications. Headphone: Speaker 40mm Mylar with Cobalt Magnet, 25 Ohms +- 15% impedance, Frequency Response 20-20,000 Hz, Sensitivity 107dB SPL  3dB at 1kHz, Input Min. input 20 milliwatts, max. 40 milliwatts, R/L Output Diff 3 dB, Distortion 5% Input Connection 3.5mm, black jacketed, nickel plated stereo, Black leatherette Earpad, Cord 7 straight, attached volume control, permanently attached for classroom safety. Omnidirectional Electret condenser Microphone, Sensitivity -38dB, standard, min -35dB, max -41dB, Frequency Range 10-10,000 Hz, Impedance 1,500 Ohms +- 15%, Operating Voltage 2V up to a maximum 10V, 3.5mm plug, red jacketed, nickel plated.