1,Ergonomics Design: The NENRENT S610 Earbud is designed according to ergonomics and the S610 is smallest bluetooth Earbud in Currently, Fits either ear, wear the bud on right ear for better call clarity. 2,Bluetooth issc V4.1 Version:Supports Multipoint Technology Can connect to two different devices in 10 meters range simultaneously. which makes it fit perfectly to your ear and comfortable. Guaranteed to be 100% secure & stable during intense exercise such as running, climbing, riding, camping and other active sports even in a rainy day. 3,Longest Service Time: Built-in high performance rechargeable Lithium-poly 60mAh battery,High capacity battery provides up to 6 hours call time and 4-6hr music playtime at 40-50% volume (adequate for home/office with little noise interference),full charge in around 1-2 hours and up to 130 hours standby time.