As with most K&F products, the build quality of this filter is quite good. The threads are smooth, the filter ring is powder coated and then the optics... well, hard to tell they're clear or anything as it's a diffusion/softening filter, but the image quality is still quite good. More about that later. The filter comes in a circular filter housing which is one of the cleanest filter housings I have ever seen! If they aren't already selling these as products, they honestly might be! There are raised dividing circles that allow you to fit filters of all sizes into the case, unlike most that have a foam cutout (which admittedly offers more padding). It would be nice if the filter housing had a little sticker stating what's basically on the box - "Nano-Series 52mm MRC Black Diffusion 1/4" in my case. In fact, the outer box has it listed a few different times , including twice on the sticker label... one on the case would be even better The optics look like clear glass with a few small gray dirt spots This is the intended design The effect it creates is a soft diffused glow ;a bloom effect.Using this black diffusion filter reduces contrast and overall it looks like a soft filter.But sharpness at the point of focus is not affected too much so they are used in portraiture as well as other creative photography Light sources bloom when looking through this filter I still find the 1/4 power very useful, while the 1/2 to 1 can be more of a niche.