A quality filter that is on par with my others. A bit stiff. All CPLs are tricky.
No problem with construction materials or very nice storage case, but as has been mentioned, it's stiffer than my other polarizers which makes it easy to accidentally unscrew it rather then simply realign it if you turn in the wrong direction!
CPLs are tricky and none are perfect - I guess it's just physics. For reflection removal, it works very well in the right circumstances (some angles to the sun work better than others). My chief complaint, and it's common to all of them, is how they affect color... a little extra saturation is nice, but they tend to emphasize the yellow and blue portions of the spectrum, sometimes creating odd gradations to the blue skies, or a slightly unnatural warm glow to the greenery. This one has those issues as well... but when used in a complementary angle to the sun, this filter provides a "mostly neutral" color and does not seem to suffer any resolution degradation.

As I said, this one matches up with the best of mine, so it deserves 4 or 5 stars. I've rounding down just because the stuffiness of the ring could cause some grief.

Sorry, these aren't professional photos, just things taken around the house, but they illustrate the functionality of the filter: (assuming they show in the original order)

1. A GOBE filter and a K&F. There is a visual color cast difference... the GOBE is biased a bit toward yellow/green, whereas the K&F is a more neutral gray with perhaps a tinge of magenta, possibly to help compensate for the polarizing effects?

2. A pool at right-angle to the sun with the polarizer attached but in the LEAST polarizing position.

3. A pool at right-angle to the sun with the polarizer attached but in the MOST polarizing position.

4. A window reflection with the polarizer attached but in the LEAST polarizing position.

5. A window reflection with the polarizer attached but in the MOST polarizing position.

6. A computer LED screen with the polarizer attached but in the LEAST polarizing position - colors should appear balanced... here they are a bit rich and perhaps a little blue, but this was in a VERY uncontrolled lighting situation so I consider the results to be fine.

7. A computer LED screen with the polarizer attached but in the LEAST polarizing position - screen should be very close to black

8. A harsh sun view of the forest with the polarizer attached but in the LEAST polarizing position.

9. A harsh sun view of the forest with the polarizer attached but in the MOST polarizing position. Sky is graduated a bit "off kilter" because it's hard to get a CPL aligned perfectly in bright sun and a wide angle can exacerbate the changing angles. Trees have more yellow in them, but the contrast is nice, so minor corrections in post could result in a pleasing outcome for a photo that would be otherwise flat.

Hope this helps!