This product is very popular, not just because of the incredible price, but also because it is so easy to use.There are two kind of sound transmission: One is Air Conduction Sound To listen via ears, which is transmitted sound through air vibration; One is Bone-Conduction Sound Directly Transmitting Sound Vibration, which is transmitted sound through bone vibration. Namely, sound is transmitted through Air Vibration and Bone Conduction, Skin Tissue Vibration. Sound with bone-conduction technology, there are many advantage. Build in bluetooth 4.0 ,mic and EDR, you can answering your phone after connecting with your phone.Also we build-in DSP smart noise reduction,better talking effects. Changeable lens,flexible design,when you want to try something else,you can buy myopia lens in the local eyeglasses stores.That's easy! Multi functions,not just sunglasses,but also smart glasses,you can use it as sunglasses,or recorder or cameras ,record every moment while traveling.What's more,we build-in DSP audio processing,enhanced audio effects. Long working time standby time but short charging time,we build-in Li-ion battery: 150 mAH(both side),Working electric current â¤20mA, music playing can last more than 6.5 hours,talking can last 10 hours,but charging can be finished in 1.5 hours.Please note that standby time:50 hours.