obviously Nikon Z-mount uses a mighty big hole. Really curious to see what the lens mount parameters really will be. Rumors are confused, especially as far as throat width [diameter of clear opening] goes. 49mm and 55mm are thrown around. I am sure, Nikon has maxed it this time, as there is no disadvantage associated. Going too narrow however, causes all sorts of limitations and problems for lens design. See narrow Nikon F-mount or Sony FE mount.