For "rev2" version You will need M3x15mm bolt and M3 nut.
Original versions flex to much when tightened so it can not hold calipers strong enough, "rev2" have additional front brace to significantly reduce flexing and makes strong connection. Also I make it slightly bigger to fit better in depth base compartment in Mitutoyo caliper box.

You will need M3x12mm bolt and M3 nut.
I made new "base_big" if you want a bit bigger and sturdier base.