This foam windshield for aviation microphone replaces the original windscreen when it is missing, torn or worn dirty. (Electret Mic Rectangular type)
Its usefulness is multiple, it reduces ambient noise and prevents air pressure to activate the microphone. Your squelch will then be set at a lower level .
The "Voice activation " ie the triggering setting voice level on your headset will also be set lower .
But one thing no one never tells you ...
The windshield actually protects your mic. On modern headsets, the electret microphone is very often found... The membrane of the microphone picks up ambient noises on both sides, then it will compensate this noise by a small capacitor, which will tend more or less this membrane.
This mic is therefore very fragile, delicacy of the membrane which is giving its flexibility makes it sensitive to high moisture. The windshield will create a barrier and will filter out the moisture from your mouth, it is indispensable.