Product review (4 stars): Reasonably-Priced Replacement Wicks for Duracraft or Kenmore Humidifiers.
Although listed as Duracraft replacement wicks AC-818/HC-818, the wicks that I received are BestAir HumidiWick D19-C (from sellers Buy-it-now-store and thepartsbiz). They will fit Duracraft humidifiers DH8000, 8002, 8003, 8004, and 8005. I'm using them in a Kenmore model 14113. They are 8.5 x 8.25 x 2 inches in size. Since the wicks fit the Kenmore 14113, they should also fit Kenmore models 14103, 14104, 14114, 14121, and 14122. I previously bought the Holmes wicks that Sears sells for their Kenmore humidifiers. The Kenmore/Holmes wicks are slightly thinner than the BestAir, but there is no practical difference in size.

BestAir puts a metallic single layer through the center of the wick, while Holmes puts a stiff black layer on one side of the wick. These things are presumably supposed to retard mold growth. Holmes uses Microban antimicrobial treatment; BestAir uses MicroFree. Evaporative humidifiers typically mold within three weeks of use, even if disinfected with ammonia periodically, so I don't know how much difference these treatments make. The wicking material in the BestAir is softer than the Kenmore/Holmes, but that doesn't seem to matter. The BestAir wicks fine, and they are less than half the price of the Kenmore/Holmes wicks, so I'm pleased with them.

I have not have any trouble with these wicks drying out at the top. When that happens, it usually indicates that something is interfering with its ability to wick, so the wicking cannot keep up with the evaporation. In my experience of over a decade of using evaporative humidifiers, the culprit has always been mold that has caused hardening in the middle of the wick. If the top of the wick dries out, flip it over. If it dries out again quickly, you need to replace the wick. Don't expect wicks to last as long as the humidifier manual says they will. They will go three weeks, at most, before molding.