I bought this filter without the knowledge of the company. I still don't know anything other than what I've observed: it appears to be of quality construction, and most importantly, I took it out to shoot and the clarity and visual performance of my favorite wide-angle Nikon lens remains just as superb as always. So a quality filter at a very good price.

I bought this for a rarely used camera. It's still a valuable collector's item that I want to keep in excellent condition and that means I had to protect the lens. I only have filters with the Zeiss "T" coating made of German Schott glass on the cameras that I use a lot because I think they are the best multi-coated filters I can afford, but I can't spend the money on them spend on a camera I rarely use.
Any camera that is threaded to accept a filter deserves the protection that comes with a filter mounted in front of the actual camera lens. I would rather risk damaging the AR coating of a filter that can be easily replaced than risk damaging the actual lens on one of my cameras through cleaning and exposure to dust or chemicals in the air.
This brand of filter came carefully packaged and the filter holder that comes with the filter is well designed and provides excellent protection for the filter when it is not on the camera lens as I am using a different type of filter. This filter has multiple AR coatings on both sides of the filter and after comparing the results of identical images taken with the same camera using this filter and one of my prized and now unaffordable Zeiss "T" filters, I can say I see no difference can the results. I'm sure an optical lab could document some differences, but in the real world I can't tell any differences by comparing the test images,
This design works so well that I am slowly replacing the older non-Zeiss filters I have on my older lenses and cameras with these newer designs.

Have now used the filter in a wide variety of situations and can only say that it is great. Top picture quality and the protection is perfect. Use it on my 24-70 2.8 Art from Sigma on my A7 III. The image quality is not compromised and the lens is perfectly protected. The processing is very good and of very high quality. Completely happy.

Both lenses are Sigma lenses with 2 different brands of UV filters on them. The lens on the left is my 150-500mm with a different brand filter. On the right is my 150-600mm lens with the K&F filter. The left lens looks a little blurry, but the K&F filter doesn't.

Doesn't reduce the picture quality I can tell. You can feel it's weatherproof, but I'm not testing it to see if it really is.

Comes in a plastic case

No complaints so far.

The K&F D-Series UV Filter is a well-made, durable optical device that appears to perform as advertised. I wish I had noticed that the NANO series filters are a little better and only a little more expensive. In any case, if you compare this D series filter directly to the B&W UV Protection Filter (010) (XS-PRO), MRC Nano, the K&F product seems to be of the same quality and performance for less than half the price .

Arrived quickly. It was exactly as expected, fitted the camera perfectly and was easy to install. Lens hood and cap both fit as before. Ideal for Panasonic DMC FZ2000

Arrived quickly. It was exactly as expected, fit the camera perfectly, and was easy to install. Lens hood and cap both fit as before. Ideal for Panasonic DMC FZ2000

Personally, I don't like using UV protection as it can distort/defocus image quality.
I invested a lot in my lens and went for more expensive ones like this one.
I don't see any reduced image quality or focus speed degradation.
Good protection / fit.

Highly recommended

Got some new RF lenses, needed the 43mil and here we go.

Great fit, doesn't interfere with retracting the R's Ben when shutting down, nice protection at a good price.

I just got a new lens, needed a 77mm filter to protect it. I'm not going to sit down and tell you that this glass is better than any other glass. I just got it and I'm not an optics expert.
But I can tell you the packaging was beautiful, the filter housing - one of the nicest I've ever seen. It is circular in shape and holds filters of multiple sizes with grooves in an internal holder. So much nicer than the big chunky square filter boxes I have from other brands.
But - the killer was the filter which was so thin - and that it has 2 areas that are knobby so you can grab it - while the rest is smooth - a really nice feature.
Seems right at home on my Canon RF24-105/4 L IS USM.
I didn't notice any difference in focus speed or aberration, but again, I'm not a lab.
I'm pretty happy with this brand. I did not expect.