Beautifully solved is to run the entire base as Arca compatible rail, ie you can move the carriage in a corresponding terminal roughly its entire length before reaches for fine focusing.
At first glance it seems a bit strange that the upper clamp is rotated by 90 °. But if one has a slightly longer Arca-plate, one can exploit the to to move the camera sideways and saves thus possibly a second, transversely mounted slides or buying as a cross slide.
The dark gray anodizing seems to be a bit thin, I hope this high-priced part is not so soon unsightly.
In the class of Castel Q is unrivaled bottom line in my opinion, so 5 stars
