I purchased the rectangular filter set directly from K&F.
Since I have worked with screw-in filters in the past and had the problem of vignetting when screwing multiple filters on top of each other, I have long wanted to purchase a set of rectangular filters.
Since sets from NISI, Haida and other well-known manufacturers are very, very expensive, as an amateur photographer I was looking for a cheaper alternative.
When I saw several reviews on YouTube, I opted for the K&F set, which is half the price of Haida and CO.
I absolutely do not regret my decision.

The filter holder is very nice and well thought out.
I particularly like the way the polarizing filter is attached to the holder and how it can be adjusted using the little dial.
The filters themselves are made of optical glass and have no color cast and are also well coated.
Another positive aspect is that the filters have a plastic frame with a tab.
This allows filters to be inserted and removed without annoying fingerprints.
A bag is included to store and transport the support and the filters it contains.
Also included are various adapter rings for different filter thread diameters.
As an amateur landscape photographer, I no longer want to do without the advantages over screw-in filters.

I give a clear purchase recommendation for amateur photographers and professionals too!
I didn't expect such excellent quality for this price.
It's crazy what K&F offers here.