Sony MDR-HW700 Wireless Digital Surround Headphone for MDR-HW700DS (Japan Import)<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>Driver unit: φ50mm Playback frequency: 5Hz-25， 000Hz</li><li>Impedance: 24Ω Power supply: Built-in Li-ion rechargeable battery (DC3.7V)</li><li>Charging time: 3 hours Charging Method: USB charge</li><li>Battery life time: 12 hours Weight: about 320g</li><li>Accessories: None</li></ul></div><img src="http://ecx.images-amazon.com/images/I/41hVSheC4BL.jpg" noproxy>