These K&F "Nano K" series filters (CPL and UV are included in this kit) are supposed to be a lower tier products than the much more expensive "Nano X" series filters. I briefly compared these attractively-priced K&F CPL and UV filters against higher priced alternatives I had on hand:

CPL filter (Circular Polarizing filter):

In a side-by-side comparison with the more expensive "Nano X" series CPL filter (which I also have), the obvious difference is that this "Nano K" CPL has bluish surface reflections, whereas the more expensive "Nano X" feature more common greenish coating reflections. (Not sure what that means in practical terms; probably not much.) In use, the polarizer works as expected. I see some color cast in images, but that's true for the "Nano X" CPL too. (Color cast in CPL is very common.) I just fix that in post, as needed.

UV (Ultra Violet) filter:

I didn't have a "Nano X" UV filter to compare against this "Nano K" filter, so I compared against a more expensive Hoya Fusion series UV filter that claims transmissibility of 99.8%. The color of the surface reflections off of this "Nano K" UV filter are similar to the Hoya filter: green. But the intensity of the reflection is stronger in the K&F UV filter than the Hoya filter, indicating better anti-reflection coating in the Hoya. But when I compared this K&F UV filter next to an off-brand UV filter, the anti-reflection coating was better in the K&F, overall suggesting the anti-reflection quality of this K&F UV filter is still quite decent.

In both cases, I am not sure that I would be able to tell the difference in a blind test (especially for the UV filter). Although I tend to select more expensive filters for the lenses I use frequently, I personally wouldn't hesitate to use these lower-cost alternatives on some of my less frequently used lenses.

I also want to mention that the craftsmanship of these K&F filters is excellent; they fit onto lenses very smoothly. As for the frame/rim thicknesses, see below for the measured thickness. (They are reasonably thin, and should work fine on most wide angle lenses.)

In the sea of crazy expensive filters on Amazon these days, the price point of this filter kit is refreshingly reasonable. I am happy to give these K&F filters 5 stars.

Frame thickness (as measured with a digital caliper):
- 67mm CPL (Circular Polarizing filter): 5.3mm thick
- 67mm UV (Ultra Violet filter): 3.3mm thick

Included in the box (67mm size):
- CPL (Circular Polarizing filter)
- UV (Ultra Violet) filter
- Lens cap with a tether
- Protective filter carrying case: A bit bulky but very nice folding case with 3 filter pockets
- 3 sealed packets of microfiber cleaning clothes