Product review (5 stars): Better than Aftermarket Replacements
I tried non-Holmes aftermarket replacement filters before trying the Holmes original replacement filters.  The originals fit the Holmes humidifier much better, last longer, and deliver more humid air.  The Holmes product can cost about the same as the generic replacement bought at say, Lowe's, but you may have to have order online to get the real thing from Holmes.  For me, any inconvience caused by online ordering is worth it for the much better performance.  The wick life can be significantly extended by using water treatment products from Holmes as well -- I find these treatments work well but do require an extra few moments each time they are added when refilling the humidifier tank(s).  One drawback to the water treatment products is their potential toxicity, which may be a particular concern for households with pets or small children.  The Holmes original filters do work much better than generics even if you don't use their life-extending water treatment products.