20 meters barrier-free reception of this K8 lavalier wireless microphone. Frequency range: 2.4GHz. Frequency response range: 20-30khz. Transmission delay: 9Ms. Signal-to-noise ratio(SNR): 64dB. Input voltage: DC 4.8~ 5.4V. Charging current: About 65mA. Battery capacity: 80mAH. Working time: About 8H. Charging time: About 80min.