I’m brand new to Zbrush, so still practicing a lot. 
In the future I would like to make some personal, fun stuff to have 3D printed. I know how to set a world scale for the scene (via Scale Master), but depending on the material there is a detail limit. Let’s say the smallest detail to be printed is 0.8 mm. How can I set my brush size to that exact dimensions, so when I sculpt in a line I know it’s not too small for instance? 