Tested the ND against a Freewell, and the UV against Freewell and the Breakthrough X4 UV filter I used to have.The Kase exhibited significantly less flare than Freewell for both the UV and the ND. Having researched both of these magnetic filter sets before purchase I wasn't too surprised by that. What shocked me though is that the Kase UV also had visibly less flare than my Breakthrough X4 UV filter. Considering the Breakthrough X4's are generally considered top-of-the-line across the board that was quite unexpected.Sharpness for all of the filters was quite good. Even with 100% crops I was hard pressed to identify any differences. My tests were shot with a Nikon Z6 and NIKKOR Z 24-70mm f/2.8. All shots were taken at f/11 so that I could use the same aperture with and without the ND's. At f/11 sharpness starts to become just a bit diffraction limited and the Z6 does have a low pass filter. However, unless somebody is using a higher resolution sensor with no low pass filter and the sharpest available glass, I doubt there will be any visible difference even at 100%.The UV's are perfectly color neutral - as one would expect. The ND's both shot slightly cool and needed to be warmed slightly - 100K to 200k on the Kase, and an additional 100K to 200k on top of that for the Freewell. Each also needed an insignificant amount of magenta added to balance it out. I wasn't shooting color cards, so I can't speak to color accuracy, but at least visually they both corrected fine.BUT... for reasons I haven't been able to identify yet, in the scene I shot to test, my test shots with the Kase did result in the camera's auto white balance being off considerably. I shoot in RAW, and when I white balanced in post I only needed to warm the image by 200K or so as noted above. However, if I use the "as shot" data from the camera for white balance, it was coming up 3000K off. Not an issue if you shoot a white balance card, have known lighting, or don't mind tweaking it to taste, but could be an issue if you shoot JPG.The magnetic attachment seems plenty strong. While there is a warning in the Kase package against using them in gale force winds, I don't foresee any issues with normal use.Note that you can NOT screw a filter onto the front of the Kase UV magnetic holder. While it looks like it has threads, the diameter is just a bit wider on the front threads, and you can't screw a normal filter on it.That said, both filters worked fine with my lens cap. Obviously can't make any guarantees about other brands or sizes.In the end, I decided to go with the Kase. I shoot RAW so I can correct color in post if I have to. That versus the flare issue with the Freewell - while most shots won't be affected by it, when it happens you can't really correct it. I also like that they went with hardened optical glass, and while I may not use the carrying case, it is a nice touch.