Driver Unit : 10mm Impedance : 16 Ohm Sensitivity : 108 +/- 3DB (AT 1KHZ, 0.5RMS) Frequency : 18-20.000HZ Length : 120mm On-Off Key Function : Click 1x : On/Off (for phone call) Stop/Play (for music) Click 2x : Next (for music) Click 3x : Previous (for music) Function of the big black key : move to"+" to turn up the volume, move to "-" to turn down the volume