Description:   Bluetooth version: Bluetooth 5.1   Music / call duration: 3 hours   Charging box can charge the headset:3-4 times   Charging box capacity: 300mAh polymer lithium battery   Headphone single ear capacity: 50mAh polymer lithium battery   Sensitivity: 120dB   Impedance: 32Ω   Bluetooth transmission distance: 10 meters   Charging voltage: 3.7V      Specifications:   1. Second generation Bluetooth 5.1 chip   2. LED smart cool button light   3. 9D stereo HIFI bass surround   4. Graphene film speaker   5. Magnetic pull-out charging box   6. Ergonomic design; will not fall when worn on the ear   7. Life waterproof; no matter whether it is sweat in the gym or outdoor sports in the rain, it will not ause damage to the headphones.   8. Support single/binaural use (left and right headphones have built-in microphones for independent voice calls)   9. The ergonomically designed headphone head with soft natural silicone earmuffs will not cause ear pain and other bad conditions even if you wear the headphones for a long time.      Package Included:   Bluetooth Headset*2 (left and right ears)   Charging box*1   Natural silicone earmuffs * 2 pairs    Instruction manual*1   USB charging cable*1