Features: BT 4.1: Support BT 4.1 transmission protocol standard, the transmission speed is faster and more stable, can effectively reduce the sound quality loss. Compatible with most smart devices with BT. Multi-point Connection/Re-Dialing : It can connect 2 mobile phones at the same time. Just quickly press the multi-function button 2 times to redial the last broadcast number. Noise Isolation: Earplugs are designed so that external disturbances can be reduced to a lower degree. Intelligent noise Isolation can make you enjoy crystal clear talking even in the open and loud environment. Endurance Time: Built in rechargeable lithium polymer battery, the longest standby time can be up to 80 hours and the time of music can be up to 4.5 hours. Clip Design: User-friendly retractable clip-on design, with the design of the clamp, it will be more convenient for you to wear it, simply clamping down on the clothes. Hold to pull ear-bud to answer the call, one click to retract the ear-bud easily when the call finishes.