Sennheiser RS 145 comfort. Headphone frequency: 18 - 21000 Hz, Headphone sensitivity: 110 dB, Total Harmonic Distortion (THD): 0.5 %. Connectivity technology: Wireless, Wireless technology: RF, Wireless range: 150 m. Dimensions (WxDxH): 85 x 225 x 133 mm, Weight: 0.43 kg. Battery type: AAA