eBerry Hands-free Wireless FM Condenser Microphone Headset Megaphone Radio Mic for Tour Guide, Salesman, Teacher, Host, Speaker, Conference and Karaoke (Black) Easily pairs to all kinds of FM supported devices such as speakers, megaphones, amplifiers, FM radio and car audio systems Large screen to show frequency; simply pair the FM microphone to the speaker with the same frequency and you are ready to go Built-in lithium-ion polymer battery supports up to 8hrs' use after full charge, rechargeable and environment-friendly for long-term use Long FM wireless transmission distance of up to 20 meters, available channels of up to 225 with no signal interference Widely compatible for teaching, tour guide, sale, speech, conference and more