The Original American Stereophone Company ,Ever since we invented the world's first SP/3 stereophone back in 1958, Koss Stereophones have been bringing back the excitement of a live performance. Music lovers around the world recognize that dedication to accuracy in sound reproduction as The Sound of Koss. , ,THE SOUND OF KOSS ,High-Resolution dynamic audio driver , ,CUT THE CORD ,Bluetooth® 4.0 Wireless Freedom , ,STAY CONNECTED ,Built in microphone & on-board controls , ,Wireless Bluetooth® - Over-Ear Headphones , ,KEY FEATURES: ,- Full size, Wireless Bluetooth® Over-Ear Headphones ,- Bluetooth® 4.0 Technology ,- D-Profile ,- Built-in rechargeable lithium-ion battery ,- Up to 12 hours of playtime (at moderate volume) on one charge ,- Up to 40 hours of standby time on one charge ,- Detachable cord ,- Fold flat for travel ,- Available in dark grey or white ,- Specifications ,- 10-20,000 Hz ,- 38 Ohms ,- 97 dB SPL ,- 4 foot ,- 1 Year Warranty