I bought the rectangular filter set directly from K&F.
Since I have worked with screw filters in the past and got the problem with vignetting when screwing several filters on top of each other, I have 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, as a hobby photographer I was looking for a cheaper alternative.
When I saw several reviews on YouTube, I decided on the K&F set, which is half the price of Haida and CO.
I have absolutely no regrets about my decision.

The filter holder is very valuable 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.
Another positive aspect is that the filters have a plastic frame with a tab.
This allows the filters to be inserted and removed without annoying fingerprints.
A bag is included to store and transport the holder and the filters in it.
Also included are various adapter rings for different filter thread diameters.
As a landscape hobby photographer, I no longer want to do without the advantages over screw-on filters.

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