COBRA DIGITAL CA MS4 Remote Push-to-Talk Microphone System Dynamic Remote 4-Pin Ptt Microphone System For Cb Radios Noise-Canceling Technology Heavy-Duty Adjustable Ptt Transmit Button Ergonomic Headset With Retractable Cord Easy To Install Dynamic remote 4-pin PTT microphone system for CB radios. Noise-canceling technology Heavy-duty adjustable PTT transmit button.