I had typed a long review that was somehow deleted on its own, so here's a shorter version.

These filters are wonderful. They feel like they're well built and the glass is of decent quality. The UV filter is clear as day, to the point where I didn't know there was a piece of glass there and accidentally smudged my fingers on it trying to feel it.
The CPL filter works great, I was able to take some nice pictures redirecting where the light reflection lays.
The ND Filter is amazing. It's adjustable from ND2 to ND400, so in theory could also be kept on the lens the entire time but the exposure wouldn't be the same. The adjusting part is smooth and feels sturdy, I wish it had a locking mechanism that didn't allow you to spin the glass 360, but that's not the biggest deal.
I also appreciate the carrying pouch that allows you to fit everything that came in the box, from the filters, to the nice added microfiber cloth for cleaning

If K&F does read this though, please make it so you can only adjust the ND filter from Minx to Max and that's it. Don't let us go a full circle to end up in the same range area anyways.