When Replacing a Standard 4 Pin Microphone, Whether it's a Cobra, Uniden. or Midland, Take the back off the Microphone and Look at the Microphone Element. It's a Round Part with 2 wires Connected.  If the Microphone Element is Small (about the size of the end of your little finger) it's an Electret Element. If it's 1 inch or larger, it's a Dynamic Element. If You Don't Have the Microphone or are Not Sure Which Element you Have, Choice Dynamic. A Dynamic Element will work on all CB Radios but an Electret Only Works on about 10%. Examples of Electret Styles are Cobra 19, Uniden Pro510XL and Pro520XL

This Microphone is an Electret Style