This is a top of the line combination filter from K&F that combines an ND filter and a circular polarizer. The build quality is excellent. The machining and anodization on the knobs is very good. The selections don't wander but they are pretty easy to move overall. The knurling on the mounting ring makes it easy to get snug enough to not spin off while adjusting the ND/CPL function. Using this filter is a little tricky though and it is not as quick as using the standard filters separately. Moving one ring, tends to move another ring so you need to hold one ring still with a finger once you make a selection, then make the other selection with the other finger. This makes it very hard to use on the go or while holding a fairly heavy lens/camera combination. It is best suited for landscapes/tripod use rather than scenes where the light is changing drastically. It can be set for a scene but changing it takes some work.

Sharpness does not seem to be affected too drastically with the filter on. There is quite a bit of red/purple colorcast though. There is quite a bit of purple/red flair that can happen when used in very bright conditions so take care to be aware of this.

This filter works as a combination filter but will more caveats than using two separate filters. It still situations where both are needed, it works well. I wish they would stick with the plastic case instead of the leather type case they used on this filter. It is bulky and just doesn't stack as well as the plastic cases. The compromises make this an occasional use filter for me but in situations where it is used it has worked well overall.