When you're in the studio, it's pretty easy to deal with pops from vocal plosives: you put a pop shield between the vocalist's mouth and the microphone. This would be impractical on stage, and although most mics have some kind of foam blocker built in, these don't tend to be hugely effective.
For just this reason, the Popper Blocker was born. Currently available from a dedicated web site, the popper blocker is a piece of woven material (which looks to be carbon fibre) that sits inside the ball head of a vocal stage microphone.
Once it's inserted, you simply leave it there. Getting it in is fiddly if you want to leave the foam in place for moisture protection (I used it with an SM58), and I accidentally pulled the foam out of the way a couple of times, which was a little frustrating. But persistence paid off, and though there are still little bass bumps from strong plosive sound and wind noise, their volume is greatly reduced. I couldn't detect much (if any) difference in frequency response or dynamic character after inserting the blocker, either, which is a rather good thing.
In theory, you could run into issues if a singer used the mic at a very acute angle, bypassing the blocker, although they'd simply be returning the mic to its stock performance.
There's not much more to be said about the Popper Blocker. If you're an engineer who regularly uses SM58s or other similar basket microphones, I see no reason not to buy a bunch of these. They're not too expensive and they do exactly what they're supposed to, once you get them in the right place. The one I put in my 58 is staying in my 58, and that's that!
$4.95 each, bulk discounts available.