The ATH-SR5BT Wireless On-Ear Headphones give you phenomenal Hi-Res Audio with the convenience of Bluetooth wireless technology operation. Up to eight devices (smartphones, tablets, music players, etc.) can be stored in the memory of the ATH-SR5BT for quick connection to your chosen devices. And adding or replacing devices is made even easier with the headphones' NFC (Near Field Communication) functionality: just touch any NFC-compatible device with Bluetooth wireless technology to the N-Mark on the headphones and the device and headphones are automatically paired and connected. The ATH-SR5BT features powerful 45 mm drivers and comes equipped with a mic and volume/control switch built into the left ear cup, making it easy to answer calls, adjust volume and handle playback (play, pause, fast-forward, reverse, next/previous track) of music and video on compatible smartphones and other portable devices. A 1.2 m (3.9') smartphone cable with mic and controls is also included to provide a standard wired connection in areas where use of Bluetooth wireless technology is prohibited, for when battery power is low, or when Hi-Res Audio (5 - 40,000 Hz frequency response) is desired. The internal lithium polymer battery provides 38 hours of continuous use (up to 1000 hours in standby mode) and can be recharged using the included 1.0 m (3.3') USB charging cable.