I shall write soon more about the holder system. For now my first impressions are very good. The holder is very solid. great built quality. I got the holder itself (that is slightly smaller that Nisi v5) a bunch of stepping rings a CPL, ND grad as well as a solid ND filter.
I hope to publish soon some nice images with the use of them.
For a video showing attempts of destroying that filter check here : https://youtu.be/cbO8RWjp12g