Product review (5 stars): Bad reviews are wrong!
I usually don't write reviews, but I felt it important to comment about the bad reviews.

The filter fits perfectly and works as intended.  The people saying it doesn't fit are either ordering the wrong filter (i.e. Puresource 2, Puresource 3, etc.) or putting it in upside down.  It is very easy to invert the filter if you're not paying attention.  Use the old filter to line up the new one exactly.  The sticker on the plate was actually upside down, but the plate doesn't even need to be used. (I peeled it off)