Sorry, I might have been a bit unclear in my description, essentially the gantry plates would be roughly 60 cm in total height. But what matters, I suppose, is that the gantry would be 18cm + two round linear rails mounted top and bottom adding a further 5cm or so to the overall height of the gantry. While the space between the non-adjustable bed and the bottom of the gantry (including the rail) is 20 cm, the free height from the tip of a typical router bit on a mounted spindle down to the bed is 15cm (when Z is in its top position). Hopefully that cleared thing up a bit!