K&F concepts. They’ve been around for awhile now, so I trust them and their camera gear.
As far as their UV filter, it’s awesome.
The packaging itself is beautiful. The box it comes with actually turns into a frame for a photo that you can place into the center of it.
The filter case is also beautifully made. Really premium feel. The package also includes a cleaning cloth.
But the filter. First off, putting it onto my lens was pleasant. The partially texture/knurled surface of the ring makes it putting it on and off easy. You can really get a grip onto the filter.
The clarity is way better than my previous cheap Hoya. This might be due to the different coatings this filter has but it’s been noticeable.
I mainly use UV filters for protecting my lenses. I’ve had a few drops and I’m always happy that I’ve had a UV filter on.
You don’t want to cheap out on a UV filter because it may affect image quality and I’m glad I’ve got this one from K&F. I’ll be leaving this on this lens forever!

I'm comparing this item KF's regular Nano filter. At the same settings on my Panasonic 85mm f/1.8, I can see more detail coming out of my lens on this Pro filter versus the regular Nano Filter. Since I love the sharpness of the 85mm, I'd much rather use the sharper filter. It's probably not a big deal to those who aren't pixel peeping but I can definitely see a difference in the hairs and I really like this filter.

I'm comparing this item KF's regular Nano filter. At the same settings on my Panasonic 85mm f/1.8, I can see more detail coming out of my lens on this Pro filter versus the regular Nano Filter.

Since I love the sharpness of the 85mm, I'd much rather use the sharper filter. It's probably not a big deal to those who aren't pixel peeping but I can definitely see a difference in the hairs and I really like this filter.

There are people that claims that when you use an UV filter on your lens, the resulting picture quality is degraded. Maybe my eyes are not that sharp but I cannot tell the difference. This one can be used to protect your lens from dust and the accidental touch with your fingertips. You can clean with included cloth or buy some of these wipes for lenses. Better destroy or damage this one and not your $2,500 lens.

The lens looks and feels nice. It seems to be of good quality and would last longer. The storage case looks elegant and comes with a wipe to clean the lens. The few pictures I have taken seem reasonable, and the lens doesn't cause any issues with the quality.

Filter is nice and I would recommend this product

K&F concepts. They’ve been around for awhile now, so I trust them and their camera gear. As far as their UV filter, it’s awesome. The packaging itself is beautiful. The box it comes with actually turns into a frame for a photo that you can place into the center of it. The filter case is also beautifully made. Really premium feel. The package also includes a cleaning cloth. But the filter. First off, putting it onto my lens was pleasant. The partially texture/knurled surface of the ring makes it putting it on and off easy. You can really get a grip onto the filter. The clarity is way better than my previous cheap Hoya. This might be due to the different coatings this filter has but it’s been noticeable. I mainly use UV filters for protecting my lenses. I’ve had a few drops and I’m always happy that I’ve had a UV filter on. You don’t want to cheap out on a UV filter because it may affect image quality and I’m glad I’ve got this one from K&F. I’ll be leaving this on this lens forever!

is reviewed:

"K&F Concept Nano-X PRO Series UV Filter 77mm, Slim Flagship MCUV Filter Protective Filter"

The filter came well packaged in elegant outer packaging. Even this made you curious about the filter with its exclusive appearance.

After opening it, you can see an elegant, very cleanly crafted leather filter protective cover.
This has a folding mechanism that closes safely and cleanly using a magnet.
There is a fabric flag on the side of this protective cover. If you pull on this, the filter comes partially out of the cover via the pull-out function, so that you can remove it very easily and without risk of damage. The filter is packed in a foil bag when delivered. There is also a microfiber cleaning cloth inside the packaging.

After completely unpacking, you can attest to the filter's high-quality and clean workmanship. The filter is free of processing or material defects. The thread of the filter can be screwed onto the lens very easily. The manufacturer specifies 0.01 mm processing accuracy. You can feel this when assembling it. There is absolutely no wobble here. This means that neither wide-angle nor telephoto lenses are affected in their original performance.

Everything works perfectly. The result is impressive.
From now on, my high-quality telephoto lens will be very well protected and, thanks to this UV filter, which guarantees 99.9% light transmission, it is optimally equipped for fantastic shots without any loss of image quality.
The filter has a double-sided 36-layer nano coating. The 0.15% reflectivity of the filter ensures the above-mentioned good light transmission. This reduces stray light very well and prevents further glare. The filter is also waterproof, dirt-proof and scratch-proof. The filter is also extremely light with a very thin brass frame. The type, manufacturer, function and serial number of the filter are noted on this.

Conclusion:
A high-end filter from K&F that impresses with extremely good workmanship and high quality.
Clear purchase recommendation despite the very high price.
I rate the product 5 stars.

Thank you for reading my review, I hope it was helpful to one or two people.

This is a great filter and fits my sigma e-mount lens perfectly! The packing is fantastic and the case to carry the filter is designed so nicely! Love everything about it!

Objectively speaking, you might ask yourself what exactly justifies this price: a filter that many photographers only use as "lens protection" and whose effect is usually not even visible in the photos. But this line of thought falls short in my opinion.

The Chinese manufacturer K&F (or Kentfaith) is no longer a cheap provider. The product range and thus the expertise includes not only UV filters but also other filters (CPL, NDF, etc.). This filter therefore comes from a group that puts a lot of thought into how to build even better filters. And you can tell that from the packaging of this X-Pro filter: