For a while I had been hesitating between several brands to choose a filter holder for ND and GND filters. I took advantage of a flash sale to buy this kit. I am not disappointed.
The set seems sturdy and easy to store.
The case, quite pretty, has 5 compartments, 3 of which, for square ND filters, are raised via a ribbon. On the back of the case, there is a belt loop and a belt loop. I would have liked a slightly more spacious compartment to house the adapter rings with the CPL filter when it is removed.
The assembly (or disassembly) of the elements is well explained in instructions in several languages, including French.

Main positive points:
No dominant color, nor loss of sharpness on the first tests carried out.
The plastic frame with its tabs to handle ND filters.
The system for installing the PLC filter on the filter holder.
the knurled button for mounting the adapter ring and for rotating blocking the filter holder.
The very accessible wheel to control the polarizing filter.
The sturdy holding of the square filter on the filter holder.
The robustness of the metal filter holder.

If you have to find slightly negative points: Keeping
the square filter a little too sturdy in the filter holder.
The click too loud to lock the CPL filter in the filter holder.
No pouch to independently protect the CPL filter in the case.
No protective cover for the CPL when the set is installed on the lens.

Very easy-to-use system
Top product
I've never regretted the purchase.
A great concept in all.

Too bad that accessories to reuse filters that we already have are so difficult to order.

The filters are great and I like the frames that make it possible to remove the filter from the bag or put it on. You also have to clean less. One small thing bothers me a bit:
With the associated K&F filter holder, the CPL (polarizing filter) is very loose. It literally rattles around when you move the camera on the tripod. But everything works as it should.

I recently became aware of the K&F filter system. What I particularly like is the frame that allows me to touch the filter without touching the glass surface. And the price is also low compared to other manufacturers.

These filters are of very good quality, but above all they are very practical and very easy to use, thanks in part to the frames and tabs they have. They are highly recommended.

This is a good kit if you need a filter system that includes ND and polarizer. Image quality is not degraded with the included filters. The filter holder is sturdy and easy to install.

The system is very well built and they sell frames to take advantage of other square filters you have from before.
It comes very well presented, in a case.

Unfortunately, the original box of the product comes with the k&f concept label directly attached to it, and opened.
Very bad on the part of k&f concept, which sometimes sends cardboard to wallpaper the house with an SD card, and in this case it is worth keeping the original box, they send it unwrapped

The system with the CPL filter assembly can handle everything I've used so far. Putting on the holder is also easy. The quality of the filters itself leaves nothing to be desired. This makes filter photography just fun!

Top quality and workmanship! It's a quality product. Price and performance totally ok.