Sennheiser MB 660 UC - Dual-Ear Headset with Noise-Canceling Microphone - Includes USB Bluetooth Dongle | Headphone Reviews and Discussion - Head-Fi.org
User manual Sennheiser MB 660 UC (English - 37 pages)
MB 660 UC MS - SENNHEISER - PDF Catalogs | Documentation | Brochures
Sennheiser MB 660 UC - Dual-Ear Headset with Noise-Canceling Microphone - Includes USB Bluetooth Dongle | Headphone Reviews and Discussion - Head-Fi.org