I have several ND filters for my gear. I buy them at the size of my largest lens and get step-up rings to make them fit my smaller diameter lenses so they're all interchangable.
This ND filter has a 9-stop range, which is amazing. I'll use an ND filter for video when outdoors to reduce the brightness and for photography for allowing longer exposures.
I didn't see any X on the lens (which happens with poorly made variable filters) and the color appears neutral.
So overall, they're great.

My complaint is two-fold:
1. There's no guard to stop the filter from being moved beyond it's desired range: When adjusting a variable filter, I'm looking at the screen for exposure, not the filter. Because the filter spins 360 degrees, it's easy to push it lower or higher than the useful range. A number of filters I've used have stops to prevent this.
2. There's no "nub" to move the filter: This is usually what helps with #1: a small metal pin that I can push with my fingers to adjust the filter. Without this nub, I've got to grab the filter like I'm taking it off to adjust it, increasing the chances that I get my fingerprints on it or accidentally do spin it off.