The Shure MC51B is a unidirectional subminiature, electret condenser Lavalier microphone. It provides uncompromised sound quality and high reliability with minimal visibility in sound reinforcement applications such as television broadcasting and stage performances. Despite its small size, the microphone's condenser element provides full, clear and natural reproduction of speech.

The MC51B Unidirectional model is supplied with two types of equalization caps for high frequency response shaping. The mild boost equalization cap attenuates the natural high frequency peak of the microphone. The high boost cap does not attenuate the high frequency peak. The MC51B mic is also supplied with two foam windscreens to minimize wind noise. Included mounting accessories consist of a lapel clip, a tie clip, a pin mount, and a magnet mount, giving the user a wide variety of options for placement.