WIRELESS STEREO IN-EAR MONITORING SYSTEM: XTUGA's 2-channel stereo wireless SEM200 in-ear audio monitoring system with Bluetooth/USB is designed for use on stage, in studio recordings, exhibitions and lectures. Sem200 wireless IEM system: No static, no latency, preset 2*100 frequencies switchable at will in the 32 MHz band from 550 Mhz-590 Mhz Receive range is 262 ft (80 m). High quality materials: both receiver and transmitter are made of metal. Adopting high quality chips, the sound quality is better.