The MM 400 is a state-of-the-art Stereo Bluetooth® headset for multimedia-capabile mobile phones. With one press of a button, you can quickly switch between calls and music delivered in superb stereo sound. The invisible high-performance microphone ensures that conversations are clear, making this headset the perfect all-in-one sound solution for your digital lifestyle. Using a closed, on-the-ear design to block ambient noise, the MM 400 is an ideal companion for the urban commute or frequent traveller. Advanced DuoFol transducers provide the kind of detail and frequency response you would expect out of hi-fidelity audiophile speakers. The easy-to-use control panel is intuitive and simple enough to operate with your eyes closed-- a common way of enjoying Sennheiser"s world-famous sound quality. The MM 400 folds up for the ultimate in portability. The replaceable battery charges via USB or a wall adapter. For situations where Bluetooth is not permitted, you can use the included audio cable for a direct connection- making the MM 400 an extremely capable wired headphone as well. Delivery includes: MM 400 headset, audio cable with in-flight adapter, USB cable, wall charging adapter and carrying case *only the latest iOS supports full AVRCP. To add AVRCP to the iPhone you may use the BTD 300i or upgrade your iOS Due to the nature of Bluetooth technology, users may experience a slight audio latency when watching video on a portable device. The headphones are working fine. This is a characteristic of all Bluetooth headsets. Latency is not an issue for audio-only use, OR when using the included detachable headphone cable for a wired audio connection when watching video.