Av-jefe Acm518-sh4 Headset Microphone Compatible with Shure 4 Pin Body Pack Compatible with Shure Body-Pack Transmitter Models: T1, ULX1, UR1, PG1, PGX1, PGXD1, SLX1, BLX1, BLXD1. (Not Compatible with Mipro, Peavey, Beyer wireless microphone system) Directional Characteristics: Noise Canceling Frequency Response: 100 Hz ~ 10,000 Hz Sensitivity: -66 dB +/- 4dB & Impedance: 600 ohm Operating Voltage: 1.0V- 10V D.C.