Astatic 636L Noise Cancelling Mic CB Radio Microphone W/ 5-Pin HR Adapter Astatic 636L Noise Canceling Mic CB Radio Microphone W / 5 pin HR Adapter ADAPTER IS A WORKMAN C4PHR5C. CONVERTS 4 PIN COBRA TO 5 PIN HR Noise Cancelling Dynamic Microphone (for close talking). Heavy duty coil cord extendes to 71/2 feet. Frequency Response: 100 - 5000 ohms. Output Level: -56dB. Impedance 400 ohms - matches 50 to 1000 ohms Bulk. No Retail Packaging