For my Panasonic Lumix G lenses, I needed two "protective filters" so that rain and fingerprints can't damage the front lenses. There are different opinions on the net about the effect of UV filters, so I don't want to say anything more about it, but there is a blue-tinted coating on the K&F Concept Pro UV filter, the delivery condition is perfect and the packaging is (especially in view of the the price) can almost be described as luxurious. A first check does not reveal any adverse effects on the image quality, and the slim design means there are no shadows on the 12mm lens. Lens caps continue to fit securely, and the lens hood also fits the lens either way. I see the handy "teeth" on the outer edge of the frame as a big advantage - finally someone has thought along! Especially with the "slim" filters, it is sometimes rather tedious to get them off again after they have been screwed "safely". There are even tools that make this removal possible in the first place. But that's a thing of the past here, with this practical ribbing on the edge it's no longer a problem. At that price you can also have one or two of these filters with you in your camera bag and when the mud has splashed you can quickly put a clean one on - just perfect!

bought three adapters with a Canon R mount (one for Leica R, one for Contax and one for Minolta MD). They all reach exactly infinity. The internal anti-reflective paint is well finished. When I check them with a caliber, the two sides of the adapters appear planar (but I don't have any wide-aperture lenses to test that on). On the camera side, they are all precise and without light leakage. On the optical side, I noticed a slight light infiltration on two adapters. Of course, I purposely searched for them by bringing a 500 lux LED flashlight half a centimeter away from the adapter. Light penetration is very unlikely in normal situations (perhaps on an easel on the beach in August). I solved it anyway with a small rubber grommet. If you're shooting freehand, that's not necessary, the hand is hiding a possible infiltration. Overall they look like good adapters to me. Due to their robustness, they can withstand lenses up to 600/700 grams. However, I would not mount lenses that are larger than one kg on the nose.

Used on Techart Pro (so not on the Leica system), very useful for adapting the M42 lenses to my Sony (the Techart Pro adapter has a Sony to Leica M connection). A bit expensive for a piece of metal, but at least it's not plastic, it looks good and isn't difficult to attach.

This adapter opens the lens of my Leica camera with a Canon lens

Compared to the Leica 2000b

Leica M ring

I ordered this adapter to continue using some old Nikon lenses with a manual aperture on my Panasonic camera. It fits very precisely, nothing wobbles or jams. I also have a very good Novoflex adapter but this one is easier to fit.

The filters fit my Panasonic camera perfectly. They make a very well made and durable impression. I am sure that with careful use and proper care they will serve me well and for a long time.
I think this filter set is a good buy and value for money.