I always get filters w/ non-slip design when it's available. It makes a huge difference. I compared it w/ Hoya HD2. I shot these w/ Canon M50 w/ Nikon 35-70mm f/2.8 AF ZOOM-NIKKOR.
1) No filter. 2) K&F. 3) Hoya HD2.
Sure, it's not a great test but I can't tell any difference between all 3 of them. The Hoya was optically as good as K&F except it was very staticky that I had to return it. I didn't like it's not non-slip either. The K&F is not staticky at all and very easy to clean. When there's no reflection, it looks like there's no glass inside the ring. Kind of like magic. It's very well made.
I use it on my Zeiss 50mm f/1.5 Sonnar T* ZM. There's no play and it fits perfectly. Very happy about the purchase.

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 filter made by another brand. The right is my 150-600mm lens with the K&F filter. The lens on the left looks a little hazy, while the K&F filter does not.

Does not decrease image quality that I can tell. You can feel that it is weather sealed, but I'm not testing it to see if it truly is.

Comes in a plastic case

was amazed when I pulled the cap off because I honestly could not see the glass in the filter itself. No matter how I angled and turned the outer ring the glass reflected nothing. It wasn't until I put the cap back on preparatory to screwing the filter onto my lens that the inner surface of the cap reflected a light directly above and enabled me to see the inner glass. I installed the filter onto a standard Nikon 50 mm lens and putting aside the question of whether to use this type of uv filter to protect your lens I have noticed no distortion or light cast in photos. Because the filter has matching 52 mm thread on the outside you can stack filters on top of it. The only problem I experienced was with the magnetic lens cap which, actually, was the main reason I ordered the filter and which I imagine is their big selling point for this line of filters. The problem is taking the cap off the filter - because the grooves on the outside rim of the cap are horizontal to the plane of the lens there is no way to easily grip the cap and pull it off. K&F should have used raised horizontal striations which would allow easier gripping and removal of the cap. After a while shoving your fingernail into the very small groove between the lens and cap gets tiring and takes longer to use than the industry standard push in tabs. On the other hand the cap snaps onto the filter quickly and securely. I have tried to show these 2 factors in the short attached video. Other than the aforementioned issue with the cap this line of K&F filters with magnetic caps are a really good fit for your photography and the K&F Concept line is frequently recognized as a high quality product. I give this K&F Concept filter with magnetic cap a solid 5 star rating.

K&F Concepts is rapidly becoming my favorite filter brand for so many reasons. Here's another product that will help that potentially. While I know everyone is down on UV filters and hates on using them because the glass is "so bad" compared to the lenses on our cameras, this filter really looks amazing both in the hand and on the lenses I tried it on. Some key points: 1. The packaging and product presentation from K&F is always great, this is no exception. 2. The filter comes in various sizes, pick the one you need, I used the 82mm for this review to fit some of my Nikon Z lenses. 3. The filter screws into the threads easily and doesn't bind at all. It feels solid and well done. 4. The lens cap included snaps to the filter with a very satisfying click letting you know its in perfect position. 5. Now you can stack other magnetic filters onto your base UV filter to add more character to your shots if you so desire. I noticed no reduction in image quality or light transmission when I used the filter. Easy one for me to recommend to anyone who would like a UV filter with some room to add on other filters. Great job K&F!

I use it mainly to protect my lens against scratches, debris.
It reduces the amount of ultraviolet light that passes into a camera.
Without this filter u will notice discoloration.
It effectively removes The appearance of blue hues bled in their photos.

I originally received just the case that is supposed to hold the lens filter but no filter so I reached out to the company and after providing some information they sent me a replacement which arrived quickly. Great company and good value for what you are getting.

Excellent. I use it on my Sigma 150-600 telephoto lens and it works perfectly. You can't see anything in the image and it feels like excellent quality.

True story: I order a lot of lens caps because I lose them constantly. I've tried the little sticky straps and I lose them too. I have high hopes for this clever system. The UV filter, which seems like a solid filter, allows the magnetic lens cap to attach securely to the filter with a pleasing and reassuring SNAP. It isn't hard to remove the magnetic lens cap, but it does take some effort, which should keep the lens cap in place. I'm looking forward to taking this out on my next shoot.

I took a couple of pictures without the UV filter then took a couple of identical pictures with the UV filter on. There was absolutely no distortion or change in quality. None at all. Pretty amazing how I didn't even notice there was anything on. This is a quality product and I am very pleased with this purchase.

Great filter with nice features at a decent price. About 3mm thick. Screws on fine. Hard case. 1 year warranty if you register your product on the website