As most K&F products, the build quality of this filter is quite nice. The threads are smooth, filter ring is powder coated and then optics... well, hard to say they're clear or anything since they're a diffusion/soft filter, but the picture quality is still quite good. More on that later.

The filter comes in a circular filter case that is one of the neatest filter cases I've seen! If they don't sell those as products yet, they honestly could! There are raised partial circles that allow you to place all sized filters in the case, unlike most with a foam cutout (which, admittedly offers more padding). It would be nice for the filter case to have a small sticker on it to indicate what is basically on the box--"NANO series 52mm MRC Black Diffusion 1/4" in my case. In fact the outer box has that listed a few different times, including twice on the sticker label... one on the case would be even better.

The optics look like a clear glass with a bunch of small grey dirt specks. That is the intended design. The effect it creates is a soft diffuse glow; a bloom effect. The contrast is lowered when using this black diffusion filter and overall it looks like a similar effect to a soft filter. The sharpness at the point of focus isn't too affected though, so it can still be used in portraiture as well as in other creative photography. Light sources will bloom when looking through this filter. I find the 1/4 strength to still be quite useful while the 1/2 an 1 may be more niche.