Product review (4 stars): Aprilaire 35 replacement humidifier water pad.
We only recently installed the water pad and found it was simple to do so.  As far as function, we are not able to assess because we do not use the humidifier in the warmer months.  Because of the ease of installing, I'm certainly pleased we changed it ourselves rather than pay a service person to do it.  I gave the rating a four star because I simply couldn't bring myself to say I love a water filter!