Have filters from B + W Hoya Pro Filter etc.
That seems to be ok. No defects noted so far.
Test will be how it holds up over time.

As expected, easy to assemble. No problems.

For the price it's great, very sharp and there are hardly any aberrations or reflections.

For the price it is great, very sharp and there are hardly any aberrations or reflections.

I almost returned it when I found out my lens came with a complimentary $50 Sigma lens UV filter. The optics on it are wonderful, but I'm about to go to Niagara Falls and I imagine I don't want to marry my lens cloth.

I thought - why not just test them both under the sink before sending it back? So glad I did!

As if by magic, this K&H filter drains and all the water disappears. The free Sigma filter? It sucks the water! And it's hard to get off!

If you received a free high-quality UV filter and stay dry 24/7, no upgrade is needed. Do you value versatility in all weathers? Buy this now!

I first bought the K&F Nano series filter for one of my lenses. I believe it was for my Nikon 80-200mm F2.8 D ED lens. This lens produces really sharp images at a distance and is not a close focus lens, even noted by Nikon. I bought the lens used and it came with a dented UV filter. I got ghosting and when I removed the filter the ghosting was significantly reduced. I ended up buying several more for my other lenses. I also use B+W filters. Well-made filters too, but a little more expensive. The K&F is by no means a $100 filter, but for the price it does what I need it to do. I particularly like the grease and water-repellent nano-coating. Worked well when I was shooting at the beach. The sea fog is easy to remove,
We really don't need UV filters anymore with digital because UV doesn't interfere with the sensor like it did with film. I just use them to avoid having to constantly clean the front elements of my lenses. I think keeping this to a minimum will prevent potentially scratching the element. I know there are a few schools of thought on this subject, but I just do what I'm comfortable with. From what I've read and can tell, the filter is glass and not plastic, which is nice these days. I have them on all my lenses now and am happy with them.

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.