SHARPER IMAGE Bluetooth Behind Headphone - Black/Black. Supports Bluetooth V4.0 technology. High Quality APTX and ACC audio. High-definition wireless stereo sound. Connect music player wirelessly to device. Built-in microphone. Answer calls while listening to music. Rechargeable lithium-ion battery. Battery readout meter on select Apple products. Sweat-resistant Aluminum. Multi-pairing feature (pair to two devices at the same time). Noise cancellation.