Wireless Microphone, Karaoke Microphone, UHF Wireless Microphone, Professional Microphone, Mic, Wireless Mic, PA Mic Wireless Microphone, Karaoke Wireless Microphone, UHF Wireless Microphone, Professional Microphone, Mic, Wireless Mic, PA Mic, Karaoke MicrophoneModel: K-820 Wireless ... 10~30h * Dual DC-DC step up circuit design for microphone * Up to 300 meter operation distance in perfect ...