1. Speaker size: 30mm 2. Impedance: 32 3. Sensitivity: 84dB (indoor) 93dB (outdoor) 4. Frequency range: 20-20KHz 5. Microphone size: 4.0x1.4mm 6. Microphone sensitivity: about -42dB 7. Directionality: omnidirectional 8. LED working voltage: DC5V 9. Working current: about 200mA 10. Headphone jack: 3.5mm 4Pin 11. Cable length: 1.5m 12. The volume limit function protects childrens hearing, with 3 pairs of creative earmuffs to enjoy the fun of DIY.