Product review (5 stars): These wicks work fine
Given that buying the official Kenmore replacement wick in a store can cost $25 and the Kenmore branded wicks can cost $17 on the net, I just had to give these a try.  Comparing to the Kenmore branded wick, this one produces the same water use rate for the humidifier given the same conditions and you can get four of them for the price of buying one Kenmore branded wick in a store.  I can't see any significant quality difference, comparing a new Kenmore branded wick to this one.  Humidifier wicks calcify more quickly than you might want, this is due to the hardness of the water that you fill the humidifier with.  The harder your water the shorter the life of the wick.  If you want the wick to last longer, you can install a reverse osmosis unit to get softer water to fill your humidifier with.  It is a tradeoff between the cost of the wicks and the cost of the reverse osmosis unit.  If you are paying for the Kenmore branded filters a reverse osmosis unit could make good sense.  The filter fits nicely in the humidifier and I am happy with it.  The humidifier has no way of knowing the condition of the filter, it uses a timer that is supposed to reset if you unplug the humidifier.  The best way to judge when to replace the filter is to just look at it with a flashlight through the plastic grill.  The calcification has a color that is easily seen and works its way down the wick from the top.  The calcification hampers the wicking of water, so once it works its way down the wick the performance of the humidifier tapers off and you need to replace the wick.  I bought four of these to spread the shipping cost over more than one filter.  The filters are individually wrapped in plastic and four fit in the shipping box nicely without being crushed.  Using a bacteriostatic treatment that is designed for wick type humidifiers will keep undesired biology from growing in your humidifier and it is a good idea to put some in once in a while.  I will certainly be buying more wicks from this source when the time comes.