Product review (2 stars): Rusts and Rots
I purchased two of these for my Holmes humidifier.  Seller was good, but product is bad.

Firstly, the picture looks like the filter is surrounded by plastic.  The product in fact doesn't have the black surround, but a metallic wire frame instead.  After a few days of use, the water turned yellow, the metal is oxidized (I assume rust), and the filter is growing some white crusty stuff.  The water I used goes through a water softener and reverse-osmosis system so it's quite pure.

I'll be discarding this and the second filter that I haven't opened.  It's priced low so it's not even worth returning.