Product review (4 stars): reduced water impurities by 60ppm
I used this to replace a GE MWF filter and this filter does just fine.

I have hard well water and I use a crystalizing water softener from clearwave although it does not change the ppm readings of the water.

I get a reading of 155-160 ppm on the water coming from my tap (no filtration). After installing this filter, the water coming from the fridge read 103-105ppm. 100ppm is considered fine quality for carbon filtered water. Not bad! I'm happy.