except the internal workings and perhaps quality or lack there of. in reading the evaluations the writer used the same criteria on each filter which in itself starts to show trends in manufacturing.
i would say it starts to show that on the lower end perhaps we have products manufactured using cost advantages (reductions) with performance being just satisfactory to the high end showing some engineering that may take them beyond just satisfactory.
i would say as a first step in product analysis not bad. gives us 2 or 3 categories to help us start the 2nd step of actual application analysis. real world testing with flows, pressure drops or head loss and other performance analysis.
IMHO i think the author made a good first step.
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