I am running this on my X100VI and really like it over other filter solutions because it -almost- appears like you have nothing extra on the lens. This also means minimum added length! The knurling of the filter matches well with the factory knurling of the lens, but the the silver finish is NOT an exact match for either the VI or the S that I own. I doubt most people would care or notice, but ye warned! Would be a perfect 5 stars if the finish matched.

Other things to be aware of:

1. K&F MRC Black Diffusion filters (such as this one) are NOT the same strength as Tiffen equivalents. I compared this to Tiffen 1/4 I own and found that the Tiffen has noticeably more halation. I think this is closer to a 1/8 Tiffen Black Promist. I consider this a good thing, because Tiffen 1/4th is too much. I said it! Fite me! :)
2. Weathersealing (specifically water resistance) provided by this and other adapters that do NOT have a gasket at the threads is questionable. Even light rain can and will easily seep through the threads and potentially into the gap where the lens moves in/out during focusing. You can fix this by adding your own o-ring; these are also available on Amazon. Search "50mm OD 48mm ID" to find something appropriately sized.
3. Another reviewer mentioned that the felt of the lens cap will "shed" because of the knurling on this filter. This is true but stops happening if you carefully twist the cap around the knurling a bit. This will pull off all the loose felt at once. I have not noticed any additional "shedding" after doing this myself. I also think this is a feature rather than a bug as it keeps the factory lens cap held in place quite securely.