I'll start by saying that, for what it is, this product is pretty good; be aware this class of device (variable ND filters) have built-in limitations.
First the good parts: the product feels solid, the knurled ring is useful for getting it on and off, and its minimum and maximum filter settings are clearly marked. I will take K&F at their word the spill-resistant coating works; it definitely does not seem to accumulate fingerprints.
Then the built-in issues: the big one being the blotchy, uneven filtration when you close it down too far (the dreaded "X" effect). On my camera (Sony A7iv with 24-105mm lens) this occurs at roughly six stops of filtering. Your mileage can and will vary, but expect to see the X at some point, especially at the wide end of a zoom. Another problem is the "roughly" part -- the markings on the filter do not necessarily correlate, at all, with F-stops as metered by the camera. They are at best approximate. A third problem is the Min/Max zones are marked but there is no tactile feedback or detent to tell you when you exceed them.
More expensive ND filters may not have these problems but they definitely come with a pricetag. If this filter works OK on your camera and lens and you can live with the limitations, go for it.