Rating: 5.0 from 5.0

Quality of workmanship: ⭐️⭐️⭐️ ⭐️
Variable: ⭐️⭐️⭐️ ⭐️
Suitability for practical use: ⭐️⭐️⭐️ ⭐️
Material texture: ⭐️⭐️⭐️ ⭐️
Price: ⭐️ ⭐️ ⭐️ ⭐️

I was allowed to test the variable ND filter (gray filter) ND3-ND1000 of the brand K&F Concept.
For me it was the first contact with a variable filter.
Accordingly, I was over the large width of the setting of 1.5 - 10 f-stops by just moving the hand lever.
As an amateur photographer, I use a variety of filters up front that I carry with me on occasions like our vacations. It may not be the same for others, but I always sweat blood when changing screw-on filters in the middle of the field, scrupulously careful not to paw at them with my fingers. As of now, the camera case is a bit lighter and it stays with a single filter. I like that already very much.
But the filter was also already delivered in a valuable box, in which there is a noble bag as storage for the filter. I guess every hobby photographer is very happy about such a noble gift. But before buying, you need to know the diameter of the lens thread you are using. In my case, I ordered the filter for my normal lens that requires a 58 thread size. On the other two lenses, 63 filters would then be used.
In testing, I was thrilled with how easy it was to adjust and the quality of performance and workmanship is exemplary. Only, it would be nice if the setting had a min-max limit. So I had to always once briefly direct an eye on the lever, whether it is also in the adjustable range.
But this is complaining at a very high level. In any case, I am happy about this great filter and that the eternal change finally has an end.

Conclusion:
Very well made, variably adjustable ND filter (aperture 1.5 -10). Recommendation!

I hope that I could be of some help to you with my review. Thank you!