And if you look at the size of the grid the keys are in (that is including the space between the keys) it is roughly 6x9.6mm
They Slim's keys are neck to neck sidewise. They are 6x6.2mm in a 7x6.2mm grid, so slightly higher grid, though the width is 35-36% less on the Slim.
The typing experience is quite different though. On one Hand you can write a-z and space text with one hand on the Slim, with no punctuation or national letters or other symbols. The Pro1/Pro1X gives a much more 'normal' typing experience, BUT is really awkward to type on with one hand only, while keeping some sort of