Built-in HD and sensitivity microphone: idea for in car calling or working use, perfect for stealth listening or watching at work. Built-in 50 mah polymer battery, up to 4 hours of continuous talk time, 3.5 hours of music time, only need to charging 2 hours, do not over 2 hours. Pairing instruction: Press and hold the button until the voice states "ready to pair" or the LED light flashing red and blue. Notice: The Bluetooth is only for one ear, not a pair, due to the difference of people's ear, this earphone maybe not fits everyone.