Polk Audio AM4219-A Hinge Wireless (Black) Bluetooth wireless technology apt and AAC delivers high-quality sound from your smartphone, tablet, or computer. Near field Communication (NFC) allows for ease and convenience of simply touching your Bluetooth device to pair and connect. 12 hour rechargeable lithium-ion battery. Built-in microphone lets you enjoy conversations via your compatible cell phone. Sound clear technology emphasizes voice quality during a phone call whether you're in a quiet room or a noisy vehicle. Included single detachable cable with inline control. The cable enables you to use your headphones when Bluetooth isn't available, or the headphone's battery has no charge. Comfortable ergonomically designed headband and pivoting ear cups. The headband uses A lightweight, yet rugged aluminum hinge that enables the headphones to fold down into a compact, easy-travel size.