i was impressed by the build quality of this filter. It has a nice heft to it without feeling heavy and I like that it comes with a rubber cap that can be left on it if you want to leave the filter on the lens when traveling. Otherwise, it comes with a plastic snap case that works well for keeping it protected.

The side of the filter has markings to show the ND strength. While they don't click into place at any given strength, the filter turns smoothly but with enough effort required that you don't need to worry about accidentally rotating it out of place once set. The marking are easy to read and align with the arrow.

I did notice a couple things about using this filter. First, it adds a slight warm cast to the image. It's fairly subtle, but you can see just a hint of a warmer, yellower tint to all the test pictures with the filter in place. The ND strength markings seem accurate, as I adjusted my shutter speed by a stop each time I changed the ND a stop and the exposure seems consistent throughout the range.

The second artifact I noticed is due to the way variable ND filters function, as they filter out polarized light. You may notice that without the ND filter and at the strength of ND 2, the greens in the trees and plants is a darker green. As the ND strength increases, the plants take on a brighter, more neon green look as the reflected, polarized light off the plants gets filtered differently. This is not something you'd see from single strength ND filters, as they don't use polarizing technology to achieve their filtration. It's not a major deal, but something to be aware of.

Overall, this is a well built filter that has a tiny bit of color shift and exhibits some polarization artifacts, but nothing that isn't out of the ordinary for most variable ND filters and nothing that would cause me to hesitate to use this on shoots. I like the feel to the rotating polarization ring, as it's well dampened and feels high quality and has easy to read markings. The 1-5 stops of range is a bit small, falling short of many other offerings from both K&F Concept's own lineups as well as many competitors. K&F Concept offers many other variable ND filters under a range of model lineups, but I'm not exactly clear on the differentiation between their different lines. But when it comes to this filter, while not absolutely perfect, it performs very well and will find a place in my kit now.