Williams AV MIC 188 Dual-Muff, Hard-Hat Headset MicrophoneDual muff, hard hat headset microphone for use with Digi Wave DLT 400 transceiver only. Specifications Element Type Electret, noise cancelling Impedance 680 @ 1kHz Signal To Noise Ratio 58 dB Sensitivity 47 dB Headphones Impedance 32 DCR Typical Rated Input Power 60 mW 100 mW Frequency Response 250Hz 4000Hz Plug 3. 5 mm stereo TRRS with 360 strain relief Ear Cushion Gel, Soft, Circumaural Color Black Approvals WEEE, CE, RoHS Warranty 90 days