Bluetooth protocol: 5.0 Channel: stereo How to use: Earplug type Single and double ears: bilateral three-dimensional description: 1. English voice prompt. 2. Send out the phone number. 3. Visualize the functions of the IOS system. 4. Answer/reject the call. 5. Redial the last number. 6. HD voice quality. 7. Solution: high-end solution. 8. Compatibility mode: compatible with all versions of Bluetooth. 9. Signal transmission channel: Cassl2. 10. Usage: Semi-in-ear style. 11. Microphone sensitivity: -42DB high-end transmitter. 12. The longest transmission distance: 10-15 meters.