The reason to choose E-MARS BT018? 1)Great Stereo Sound with Powerful Bass. 2)Soft memory earmuffs reduce noisy and enhance bass. 3)Bluetooth fast and stable connection. 4)Comfortable Flexible and Stretchable. 5)Premium Package and Accessories-1 year warranty and 30 days hassle-free return. Technical Specification: -Bluetooth Version: V4.2 -Support Profile: AVRCP.TS.1.6.0/A2DP.TS.1.3.1/HFP.TS.1.7.0/RF.TS.4.2.0/BB.TS.4.2.0 -Working Distance Range: 32.5 feet -Frequency Range: 2.402GHz-2.480GHz -Battery Specifications: 3.7V, 300mAh,Lithium-ion battery -Charging Voltage: DC4.2 - 5.5V -Charging Time: <3 hours -Talking/Music time: about 6 hours -Standby Time: 98 hours Package: 1 x bluetooth headset, 1 x user manual, 1 x USB cable, 1 x Aux-in cable. Notes: -If bluetooth fail to connected, please restart.If it's still unconnected, please refer to us.We will reply in time. - It is not collapsible. -It is passive noise isolating, Not active noise cancellation(ANC), it can't cancel the noise completely. -If you feel a little tight which is designed to isolate noise.Please take it off to get your ears relax and protect them from lasting muggy for a while. -Please make sure the software of device is fully updated when connecting . -Please charge the headset after a long time none-use. -Do not perform other operations when searching Bluetooth to prevent the program error. -Please select a proper volume while using to protect to your ears.