I've had these for nearly three years now for my B112 and B112MP3 speakers and they are in and out of the car several times a week, taking the PA to and from school. They do the job really well - despite being lugged around and bumped in and out of the car boot, the speakers have barely a scratch on them.
Pros: They are good quality material that lasts. They fit the speakers perfectly, you can carry them by the slit that goes to the inbuilt handle on the top of the speaker. Don't know if it's waterproof, but it certainly keeps drizzle off.
Cons: I'd have loved a speaker bag, as the speakers only have the top handle, which can be a bit annoying to carry with, though they are quite light speakers, but there isn't one that is made for these speakers. So the cover is the next best thing.
Basically these covers have hugely extended the life of my speakers, are snug and quick to slip on. Do the job they're made for.
