Transparency note: The product was made available to me free of charge as an evaluation sample, free of any influence or expectations. My rating is based solely on my personal assessment and experience of using the product. Evaluation: For the quick readers I anticipate my evaluation, below I explain the details of my decision-making, my impressions of the product. I only take a minimal point deduction and award 5 stars, i.e. 5 stars rounded up. My only criticism is that the filter is slightly too stiff to turn, i.e. its operation when it is screwed onto the lens, but I hope that will settle down a bit over time. No, the rotation is not difficult, but a bit tough, I expect a somewhat smoother movement here. Processing quality: The slim frame is of very good quality, precisely processed and varnished. I appreciate slim filters, they don't build up as high on the lens and thus don't limit the angle of view, especially at the extreme wide angle. Slim filters can have the disadvantage of being more difficult to handle because the grip ring is very thin. Here it is helpful if it is handy and that is exactly what the K&F filter is. I can grasp the filter very well and see no problem even with wet fingers. The glass in the filter is very high quality, optical glass, very precisely processed and absolutely flat, and also multiply coated. First take the filter in your hand and see through it, preferably against strong contrasts and straight lines, for example a facade. Here you can see that you don't see any interference. I don't see any distortion, the image is absolutely flat on the entire surface of the filter, and I don't see any color distortions, I'm very satisfied. It doesn't look any different when I screw the filter onto my lens, but here there is another aspect, possible reflections, but this is exactly what a polarization filter is supposed to eliminate. In terms of the image effect, this is absolutely indisputable, be it on the water surface or on panes, reflections are suppressed very well, as expected. But there is another aspect and that is the reflections on and behind the filter towards the lens when backlighting from small point light sources is incident at an acute angle. I don't observe any reflections here, which speaks for a very good coating and glass quality of the filter. I was pleasantly surprised by the packaging of the filter and that starts with the attractive outer packaging in a high-quality slipcase. It contains a flap case with a magnetic clasp, it is very decorative and practical, and is of significantly higher quality and classier than the widely used plastic boxes. Conclusion: The K&F polarization filter is not a bargain at currently just under €150, but it is inexpensive in the truest sense of the word and is clearly placed in the premium segment. The processing quality itself is just as impeccable as the optical imaging performance on the lens. The case that comes with it is very attractive. Only the somewhat stiff adjustment of the alignment slightly disturbs the overall impression, so I subtract half a star for this. In the overall impression, this only plays a subordinate role and leads me to an almost unreserved purchase recommendation. Thank you for your attention in reading my review. If you want, please give me feedback on it, I'm happy about it.