Good seal.

Bugs won't stay sealed, so they're useless to me

Only gripe I have is you should trim the plastic flashing at the seam on the lower end to make a better seal in the bung

Fit great into my glass carboy with a tight clean seal.

Because of its rigidity, it is very hard to get a secure seal.

but, that plastic flex a bit do make sure you have a good seal.

They are not rubber, but some kind of plastic that doesn't make a good seal, and actually pushes itself up out of the neck of the carboy

Don’t waste your money and effort in this piece of junk as it will not stay in your bottle top!

it works as it should.

Works as you expect

Work exactly as I’d hoped.