Sennheiser Stereo-Headset MM50 2,5 mm Motorola. Cable length: 1.3 m. Headphone frequency: 18 - 22000 Hz, Headphone sensitivity: 106 dB, Impedance: 16 Ом. Microphone frequency: 80 - 15000 Hz, Microphone sensitivity: 42 dB. Compatibility: Telephone