Product review (5 stars): Great product (if you get the cotton type)
This product comes in one of two ways:

1 - A box with six plastic bags in it, each containing 2 absorption pads.  The pads appear to be made of cotton.  These are made by Kaz and sold under different brand names such as Vicks, Honeywell, etc.
-or-
2 - A plastic bag which contains 12 pads.  The pads appear to be made of polyester (or similar plastic) and are more airy, whiter, and a bit thinner.  I personally did not like idea of using these.

What you get depends on the seller but I now buy from DealYard because so far they have given me what the product listing indicates.

This review is for the 1st kind; the cotton ones:

The pads work well and are worth using.  They do not stop the hard build up but seem to slow it down significantly.  In my case where the water quality is bad, they are saturated and turn hard about every four days and I can do a good number of turns without feeling the need to soak and scrub the metallic part of the humidifier.  I would say a week was the max before I discovered how bad the water was and started using the pads.  So things are lot easier now.

My humidifier is also the Vicks which takes smaller pads than these.  These pads can be cut to size or put in like a pie crust.  I put them in like the pie crust.  The humidifier has been working just as well with the larger pads and since there is a lot more material, I get more work out of each pad.  The over-sized pads have worked great and turn hard completely, even their folded parts.

Over all, with these pads I've been happy with my warm mist humidifier.  I think the humidify it produces is better than the cold mist one I had before, there is no white spec buildup around it, and the cost is lower over all.  My water quality is bad and 12 of these do outlast and are cheaper than 1 filter for my last humidifier.

Again, this review is for the denser, more tan colored cotton ones, not the whiter ones.