Signal 21 M4 shoulder microphone from Code Red compatible with a variety of Motorola radios. This Signal 21 M4 shoulder microphone from Code Red is compatible with a variety of Motorola radios. It uses high quality materials that are water, wind, dust and impact resistant, making it durable. Weighing only 3.6 ounces, it is lightweight and fits easily into the palm of your hand.table.productattributes, .productattributes td { border-bottom: 1px solid #ddd; border-collapse: collapse; padding: 2px; text-align: left; }