(Built-in charging case): Headphones up to 4 hours of continuous music playback and 16 hours of maximum playback using a small charging case. Playback time varies with connection conditions and conditions of use. (Industry-leading Noise Reduction for Phone Call)Created by tech giant Qualcomm, latest cVc 8.0 Noise Cancellation technology can filter the surrounding noise and precisely pick up your voice during phone call even in places like street, office and traffic. Mics are installed in the tails of each earbud also ensure the best possible call quality. (Smart button Control) With ergonomic and sport redesign, earbuds can fit and stay secured in ear canal even with intense movement. Together with smart button sensors, you can conveniently answer calls, skip through music and access other functions at the touch of a button. (Easy to use): The twin mode/single mode make you can use either of them as you like. You don't need any skill to use the headphones. Once open the charging