Product review (5 stars): Great Cartridges
Without these cartridges to filter out the minerals/impurities in my hardwater, I would simply be throwing back "polluted" water back into the air during the winter.  My apartment is so hot (base-board heating), the temperature is actually over 90 degrees, and very dry.  I can only get these cartridges on line as the store where I originally purchased my humidifier no longer carries them.  Amazon's supplier was so quick, I wasn't expecting it.  It took no more than one or two days.