The Shure GLXD4 Wireless Receiver System features intelligent technology and smart power options that put reliable, professional caliber digital sound in the hands of performers everywhere. GLX-D Wireless Systems feature LINKFREQ Automatic Frequency Management, making it easy to rely on seamless, crystal-clear audio. GLX-D Wireless Systems feature LINKFREQ Automatic Frequency Management, making it easy to rely on seamless, crystal-clear audio. GLX-D transmitters feature best-in-class lithium-ion batteries that quickly recharge using the charging port on the receiver, or a variety of optional USB connectors. Staying ready for the show has never been simpler. The legendary Shure SM58 vocal microphone is designed for professional vocal use in live performance, sound reinforcement and studio recording. Its tailored vocal response for sound is a world standard for singing or speech. A highly effective, built-in spherical filter minimizes wind and breath "pop" noise. A unidirectional (cardioid) pickup pattern isolates the main sound source while minimizing unwanted background noise. Rugged construction, a proven shock-mount system and a steel mesh grille ensure that even with rough handling, the SM58 will perform consistently, outdoors or indoors.