z axis holes

What size drill bit should be used for drilling the holes in the two poles for the z axis. i see it says 5mm-8mm. but im not understanding that.

Basically it doesn’t matter, you are using either a #6 bolt (3.3mm) or a 3.5mm bolt. So long as it isn’t a huge hole it will be fine.

And the locations are on the assembly/conduit page.