That thin layer of foam

[mbenny123]

I've noticed that most, if not all, of my dynamic mics have this. I'm talking about that foam that's stuck to the inside against the wire mesh that you can see if you unscrew it and look inside.

Is it simply a windscreen?
Added to muffle the high frequencies?
What would happen if, say, I took it off? Would it be bad for the mic?

My concern is, I recent bought a new kick mic(Shure PG52) and I noticed it had said foam piece. I also noticed that when I put the unscrewed cap with the foam in it between my ear and the mid on my stereo speakers, I could definitely hear a difference in the highs.
I guess this might be ideal for a kick to reduce bleed, but like I said, I've noticed this same foam in all of my dynamics; vocal mics, tom mics, etc.

[mshilarious]

It's some protection against wind noise/plosives/etc. It will attenuate highs a little, mainly really high highs above 15kHz. Depends on the density of the foam, thickness, etc. It also keeps dust and dirt and spittle off the diaphragm.

[Richard Monroe]

You'll find the same thing in a lot of condensers, also, and with certain models of mics, it is overdone. AKG Solidtube is famous for this, and ripping out the foam vastly improves the mic's performance, especially if the foam is old. It tends to harden with age. Most mics sound better with the foam removed, but as noted above, this can make the mic vulnerable to dust, spit, etc. Whether you remove it or not is a decision that must be made on a case by case basis. If you do, I would say- keep the mic in a clean case when not in use, and always use a pop filter if used for vocals. It will also make the mic more susceptible to wind noise, so if it's used outside, use an external wind screen.-Richie