This circular polarizer is a high quality item. It seems to be precision construction, threading smoothly onto my lens. The glass seems sturdy and hopefully scratch resistant. When threaded on tightly, the end of the filter rotates to allow you to choose the angle of polarization. The movement is quite snug, but I suspect it will slightly loosen over time. It wasn’t so tight as to not be able to rotate with a deliberate touch.

The polarization worked as expected, reducing glare on the water and also affecting the blue of the sky. You can see this effect in the two still images as well as in the video where I rotate the filter.

Strongly recommend.

I have a small lens that is prone to flaring without a hood, so the usual step down rings with my filter(s) was a no go.
I like K&F and have used their products over the years with no problems. I ordered the 49mm to solve my flare problem.
It comes in a unusual circular plastic case, not the typical clamshell filter cases or the cheaper clear circular cases. The really interesting part is on the inside. Someone had the wherewithal to install two rubber(silicon?) grip pads...so no matter what size filter is inside...it won't move around within the case.
I'm not sure the case itself is going to hold up though...I had a semi difficult time trying to get the case to close securely...you have to...well...I had to mess with it a bit. Something they can improve on.

Cases...meh...how is the filter. It's very good. It's low profile...my lens hood doesn't even know it is there. The filer has great knurling around 75% of the filter, and has enough thickness that you won't have any trouble finding it without looking...if you need to adjust (if you have a hood with a finger slot that is).
The CPL turns smoothly and easily with zero slop. It won't move unless you want to.

I have included two images of a reflection in one of my bird baths...as you can see...it does a great job at cutting reflections. I will say it is not the strongest CPL I have...but that's not a bad thing either. I have some that are like rocket fuel for a go cart...simply too much. This CPL is balanced...and I did not notice too much light drop off at all when adjusting polarization. I had to use the reflection to find the strongest position for the filter.
It's a well balanced CPL...not too much...and just enough. It gives good saturation without knocking your colors about.

It's worth the coin...thumbs up!

Using this with both an adapter for my iPhone and with an anamorphic lens on my FX30. K&F filters are top-notch and my go-to when shopping for filters. They have supplanted other first-choice brands for filters that I have turned to in the past. Their selection is great and they seem to have a solution for whatever effect you are looking to achieve at every price point. Spend what you can (will) and you will have the best quality filter at that price point. The Nano X models are a great value, I own another Nano X ND filter from K&F along with other K&F models. All their products are of high quality, no need to worry about "buyer's remorse" with this brand.

I needed a new circular polarizer for one of my Sony lenses that is 77mm, so ordered this K&F Concept filter because I have had good experiences with this company in the past. This filter is very nice and the package screams quality when you first take it out of the box. Even the little storage case is nicer than some of the other filters I have purchased in the past. There are some nice grips on the side of the filter and the friction to turn the filter effect has a very sturdy feel, definitely not cheap feeling. The threads to screw on the filter are good and I had no issues screwing and unscrewing the filter, although turning the filter effect I did unscrew the filter a couple of times because it is a little tough to turn. Image quality is excellent, and the glass is very clear. This filter is a good one.

The circular polarizer work as it should, the surprising part is the case for the filter is very useful for storing different size of filter, so I would keep it around.

ALL IS OK.

Everyone needs a circular polarizer in their bag. K&F Concept delivers high-quality glass and protection from the elements. Highly recommended!

I like to shoot time lapse of the sun. So I use a CPL for detail in the sky and water as well as trees. This one as been lovely to use. I like the build quality I think the new case is awesome. This has been a treat to use. I think the filter is a great value for both price and the quality and features it provides.

Great quality, looks nice and feels well made. I’ve gotten products from this company before and this is on par with the level of quality they’ve provided with other products

Toller Filter sehr gut verarbeitet........!