Product review (4 stars): Metal frame may or may not be better. I have an older Holmes and, this was the type that came with it new.
I have owned every type of replacement wick for a Holmes humidifier. Plastic, with color change. Different brands over the years.
This one is my preference because the metal mesh frame just seems to fit better when inserting it.
However, I have not tested this one yet. So in about 9 months, I will revisit this review if it is no good or problems come up.
It is important to use the bacteriostat treatment and clean the tray regularly or, these things can get gross. I use my humidifier from about November to March almost 24 hours a day. I did not need to change this until the end of the season. Then I tossed it. So one of these a year, with bacteriostat is all you need. Otherwise, I'd use 2-3 a season with cleaning and change every couple of months for sure.
Tip: my older humidifier fan got dirty. So end of season, I carefully removed the screws (needed an 8 inch Phillips to do it) that holds the fan to the base and wiped it all down with a green style cleaner. So you don't need to toss a humidifier with fan parts and chamber that are dirty. Just go buy or borrow a cheap long Philips and clean it up yourself!