Sony MDR-RF840RK . Ear coupling: circumaural, Headphone frequency: 20 - 20000 Hz, Driver unit: 40 mm. Connectivity technology: Wireless, Wireless technology: RF, Wireless range: 100 m. Dimensions (WxDxH): 112 x 245 x 310 mm, Weight: 0.3 kg. Battery life (max): 28 h, Battery technology: Nickel–Metal Hydride (NiMH), Battery type: AAA