K&F Concept's range of filters have never let me down and neither has this variable ND3-ND1000 ND filter.

This filter maintains accurate color throughout the entire range unlike other filters I've used, which is a huge plus since it saves me time in post by not having to mess with color correction.

There is no dreaded "X", even when I intentionally went too far. While I'm not sure the stated range is entirely accurate, it is close enough and provides a ton of functionality, especially given the low price point compared to other filters that offer such a great density range.

I don't experience any vignetting with this filter, which isn't as slim as others I've used. But I rarely get vignetting when using the 18-140mm lens that I tested this filter with so my experience may not be applicable to different lenses.

Stops are clearly marked on the filter, and the adjustment is smooth with a little resistance that offers good control while shooting.

That said there is one thing you should know about this filter - YOUR LENS CAP WILL NOT FIT. I wish they included a lens cap with this filter or at least stated this clearly in the description, because you'll have to either print a new lens cap or buy one that will fit over this filter.

For the 67mm filter, you'll need a 72mm lens cap.

Overall this is an excellent value for a high quality filter. I doubt you'll find another variable ND filter with this range and at this quality for a lower price.