I bought the rectangular filter set directly from K&F.
Since I worked with screw filters in the past and had the problem with vignetting when screwing several filters on top of each other, I wanted to buy a rectangular filter set for a long time.
Since the sets from NISI, Haida and other well-known manufacturers are very, very expensive, I was looking for a cheaper alternative as a hobby photographer.
When I saw several reviews on YouTube, my decision on the set from K&F which is half cheaper than that of Haida and CO.
I have absolutely no regrets about my decision so far.

The filter holder is very high-quality and well thought out.
I particularly like how the polarizing filter is attached to the holder and how it can be adjusted using the small wheel.
The filters themselves are made of optical glass and show no color cast and are also well coated.
It should also be positively emphasized that the filters are provided with a plastic frame with a tab.
This allows the filters to be inserted and removed without annoying fingerprints.
It comes with a bag to store and transport the holder and filters in it.
Various adapter rings for different filter thread diameters are also included.
As a landscape amateur photographer, I no longer want to miss out on the advantages compared to screw filters.

I have a clear purchase recommendation for amateur photographers and professionals!!!
I wouldn't have expected such excellent quality for this price.
It's amazing what K&F delivers here.