Sennheiser MM 550 Travel Bluetooth Wireless Headset - NoiseGard 20 noise-canceling technology actively reduces up to 90% of outside noise, Stereo Bluetooth wireless technology delivers hands-free convenience and hi-fi sound, TalkThrough technology: one press of a button activates external microphone, Invisible microphone for taking calls in between play lists and songs, Neodymium magnets and patented Duofol diaphragms deliver excellent sound reproduction.