The case is surprisingly high quality and the filter is not badly made.
Everyone praises this product for its high quality and precision, but it is quite expensive.
It would be better if it was priced a little cheaper.
The slider allows you to change the filter, so there is no need to carry around multiple filters, which is very convenient.

To capture colors more realistically and in more detail, you sometimes have to increase the exposure time a bit without overexposing the images.
With the K&F Concept ND filter, you can reduce the brightness incredibly easily and in a very short time.
The 58 mm version screws perfectly onto Canon lenses. It's a shame, however, that the lens cap doesn't quite fit.
The adjustment lever is at the bottom right for the slightest darkening and slides upwards; for the greatest darkening, it points to the top right. For me, as a right-handed person, this is very easy to handle.
I think the results speak for themselves. I'm still a long way from being a professional, but it allows you to capture and preserve really beautifully intense colors. For a near-beginner like me who likes to try out all sorts of things, the filter is easy to use and absolutely fantastic for the sunsets we see on our Baltic Sea beach (but of course also where there isn't a beach).
The included filter case rounds out the package nicely. It's perfectly protected whenever it's not mounted on the lens, and the pull loop makes it easy and elegant to remove from the case. The leather case has a hidden magnetic closure, so the filter won't accidentally fall out.

All in all, a great filter whose results already make you want to try the next, stronger filter.