Product review (4 stars): Perfectly Good Replacement Part
This is the replacement filter that needs to be replaced periodically.  Once you install it, it needs to have about one gallon of water filtered through it BEFORE you use the water.  This is basically a flush of the system.  Once done, the water is fine for drinking.  Each filter lasts us several months.  Of course, this will vary, depending on how much it is used.

Incidentally,at the time of our purchase, the filter on Amazon was less expensive than getting it from the manufacturer's site.