Product review (3 stars): Possibly Used Filters?
I have bought 2 replacement filters from Amazon and most recently picked one up from Lowes.  The one I bought from Lowes was a couple of dollars more expensive, but it came with more peace of mind. I'm not certain that the ones bought off Amazon weren't previously used.  When you insert the new filter in your refrigerator, the first gallon or so comes out very cloudy.  This is normal as the instructions say that you should flush 3 or 4 gallons before drinking water that has flowed through the new filter.  When I installed the filters I bought from Amazon, there was never any cloudy water.  This is why I believe the filters I received from Amazon were previously used.  I love Amazon and do not particularly like going to B&M stores, but this is one item that I will continue to buy from hardware stores instead of Amazon.