Product review (1 stars): Don't work!
These granules do absolutely nothing!  I tested the water in the tank with a TDS meter.  The amount of total dissolved solids (TDS) was nearly the same after passing through the granules (within the margin of error for the TDS meter and variation of TDS's in the flow of water).  I had a white residue (minerals from the water) form all over my furniture.  It was even in my cabinets!  I switched to using a DI Resin (also found here at Amazon) and now the TDS's in the water is almost nothing.  After a couple of months of running my humidifier, there is no white residue on my furniture and the humidifier doesn't need to be cleaned (little mineral buildup on the inside).  I am sure that it will need a cleaning at the end of the dry season.  Another thing I did was drill a hole in the top of the cartridge and installed a stiff tube to allow the air that comes from the front chamber of the base unit to the tank to replace water as it is needed.  The tube is just long enough to reach the top of the tank when the cartridge is installed.  The tube stays above the water level.  I believe this to be a design flaw of this unit.  Without this modification, there is no reason that water would travel through the cartridge instead of the six or so big holes on the top of the cartridge (path of least resistance).  Downside:  you have to keep an eye on the TDS's each time you fill your tank.  Replace the DI Resin when the TDS's rise sharply or you get a smell from your humidifier.  For me, it is once a week based on the amount of TDS's that are in my city water supply.  Your mileage may vary.