Product review (4 stars): Exact replacement for Aprilaire
I was happy to find an exact replacement for our Aprilaire humidifier.  These fit right into place.  The vertical pad humidifiers, in my opinion, are much better than the old-style drum humidifiers where the drum sits in a pan of water.  With this vertical models, the water just drains out and there isn't a pan of moldy water sitting there.