Code Red Headset SIGNAL 21-M4 Microphone Signal 21 microphone has been manufactured using the highest quality specifications to be water, wind dust & impact resistance. Small but mighty. The Signal 21 fits perfectly into the palm of your hand and weighs just 3.6 ounces. With features includeing a covered audio jack and rotating clothing clip, this is one quality shoulder microphone no officer should be without. Compatible with Motorola and Kenwood radios.