Product review (1 stars): These are just like a big wet useless diaper.
These are the absolute worst.  When you put them in the humidifier they immediately sag like diapers.  The light that indicates out of water never goes off.  The humidifier does not work with these.  They are an absolute and complete waste of time and money.  Do yourself a favor and DO NOT PURCHASE THESE.  Even if they are they only ones available, don't buy them.  You will be sorry.

The best ones (and the only ones that work, in my experience), are the ones with the black plastic mesh outside.  This is what keeps them standing upright.