I've known K&F for a while now and own a few of their products (UV filters and camera backpacks). For me, the brand has always offered good value for money and is more in the mid-range price segment.
Now, however, they're looking to take things to the next level and are moving into the high-end segment.

An ND filter reduces incoming light. This filter can be adjusted from ND2 to ND32. This makes it ideal for long exposures and for "artificially" extending them. This allows for beautiful, soft gradients, especially with moving scenes like rivers, waterfalls, traffic, and other subjects.

The filter comes beautifully packaged and is a real joy to unpack. If you love unboxing, you'll really enjoy this.

The filter comes in a fabric/leather bag. It's very nice in itself, but in my opinion, a filter sits more securely in the familiar plastic cases.

The inside of the packaging can be converted into a "picture frame." It's a funny idea, but I think there are nicer ones.

But let's get to the filter itself. Here I have to say that the performance matches the price. Impeccable workmanship, both in the filter thread, ring, and glass.
The filter is easy and smooth to screw on and off, which is indistinguishable from cheap filters.
The glass is of the highest quality, and its optical performance is indistinguishable from that of other ND filters from well-known competitors.
This gives you a uniform darkening across the entire image and steps without any loss of quality or color cast.

So, all in all, a very good filter in terms of its quality and optical performance. Its weak points are the somewhat loose attachment in the storage bag.