Product review (1 stars): Don't bother
Don't bother with ordering this filter if you are searching for one to fit the Reli-On Humidifier PCCM-840.  This filter is too wide and not tall enough.  You need 4x5.5 or 6.  I went to Wal-Mart and found the right filter--two per package at $6.44 or so.  The quality of this filter wasn't near as good as the Wal-Mart one either.  This one did not have the stabilizer in the middle.