Sennheiser MM 550-X Travel. Device connectivity: Wired & Wireless, Device interface: Bluetooth/3.5 mm, Frequency band: 2.4 GHz. Ear coupling: circumaural, Acoustic system: closed, Headphone frequency: 15 - 22000 Hz. Microphone frequency: 100 - 10000 Hz. Talk time: 20 h, Battery technology: Lithium Polymer (LiPo), Charging time: 3 h. Weight: 179 g