Product review (5 stars): Works Perfectly for My Aprilaire
My wife and I had never changed the old pad in our whole house humidifier.  I figured it was time, given the crusty accumulations on our old pad.  Before we changed the pad, I have to say that the efficiency of our humidifier wasn't as good.  It seemed to take days for the humidity in the house to go up when I would adjust the humidistat.  After changing the old pad, the efficiency was noticeably better right away.  Adjustments resulted in changes to our household humidity in less than 24 hours.  If you are like me and you are wondering how much of your pad actually gets replaced, you will find that the pad in your humidifier actually has a black frame that comes apart.  This is the frame that has the water line attached to it.  Once you open the frame, you can discard the mesh metal pad and insert this new pad.  It will fit perfectly.  I'll be coming back for more of these in the future, and I would highly recommend them to anybody.