Product review (5 stars): Necessary
I hate my humidifier design because these trays keep getting caked up with minerals to the point where the wicks don't work and the water starts leaking out of the humidifier and spilling on the floor next to the furnace.  I used to try to chisel out the mineral deposits, but had poor results. These replacement trays solve that problem.  If you own an Aprilaire, Bryant, or other humidifier that uses these trays, then you had better keep these replacements handy.