Master built!, this is worth several times more. At least with this one I can actually see a difference, I have 23 years in photography and do celebrity shows.

I'm happy with the results of this CPL filter. It's well made and screws in smoothly. Adjustment takes some force, but it's also to prevent it from drifting or getting bumped. I didn't notice any appreciable reduction in image quality.

I needed a polariser for shooting some vehicles and I came across this one and took the chance on the brand because it had mostly good reviews.

After using it for myself I can vouch for the quality of the filter. There was no noticeable colour casts, reflections was removed and there was no noticeable degradation of the image quality even shooting on my A7RV which it’s big megapixel count.

Nicely done K&F I will certainly invest in some more of your filter products.

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.

PROS
-good polariser (not the most powerful, but it works)
-low-profile, doesn’t vignette on my wider lenses e.g. 16-35mm (I have the 82mm version of the filter, which I sometimes use with step-down rings).
-almost no colour cast
-good case (though I keep mine in a filter holder bag, with my other filters)

CONS
-aluminum filter ring (not brass)
-knurls for turning could be more prominent, so I can use it with gloves on (some of us shoot in the cold!).
-a little tight, worrisome for a circular polariser (as there is less ring to grip to screw it on and off. I need to be careful).

MY STAR RATINGS:
1* substandard, mostly cons
2** barely acceptable, cons outweigh the pros
3*** meets the basic requirements, cons balance the pros
4**** good product, pros outweigh the cons
5***** exceptional, all (or almost all) pros

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!

I needed a CPL filter for a lens with a 77mm filter thread. This one fits perfectly. All the threads lined up and it installed easily. It does a great job polarizing the scene so I can get photos without reflection on water and other surfaces. I was trying to catch some photos of salmon migrating upriver, but the weather hasn't been cooperating. I hope the water clears soon so I can try again. It's a great lens filter for this because it lets you see the fish under the water much better. The quality of the filter is great. It is sturdy. The glass is clear with no defects. I am very happy with it. It comes with a nice storage case too, to protect it when you are not using it.

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.

I’m really impressed with these filters. They’re well-made and work great while not having any kind of weird color cast on the image. I’ve been using this on a Canon 24mm f1.4 lens for both photos and videos and I’ve been really happy with the results. Highly recommended.

This a solid CPL filter. Quality is excellent all around from the threading to the glass. Its performed as expected at reducing glare. Case is of really good quality as well and has protected the glass nicely. I haven't run in to any issues with fitment so far, easy on easy off. Impressed with the results I've received so far.