Built-in rechargeable battery provides up to 15 hours communication time or music playback on a single charge. Bluetooth wireless headset function with a transmision range of up to 30 feet (10m) for total wireless convenience. Built-in microphone lets you talk hands-free on your smart phone or tablet. It works with online voice or video chats on PC or notebook. Built-in Microphone Invisible microphone with high- performance sound quality for clear conversations