The Shure BETA 181/BI Bidirectional Condenser Microphone is a compact, side-address microphone capsule designed for professional studio, broadcast, and live sound applications. Featuring a true figure-of-eight (bidirectional) polar pattern, it captures sound equally from the front and rear while rejecting audio from the sides, making it ideal for duet vocals, mid-side stereo recording, and controlled room ambience capture. Part of the modular BETA 181 system, the BI capsule delivers exceptional clarity, low self-noise, and high SPL handling, with a robust design suited to demanding professional environments.