If you use mm as Moi works with 0.001 precision unity you lost some point decimal internal for nurbs functions / meters for example
So better use No Unity System during work and at the end retake mm for real measures
It's the same in some program !

Hi Pilou, it doesn't really matter which particular unit system you use - the unit system is just a label.

It matters more whether you use particularly large or small number values, like if you have coordinates like 10000000000.0 or stuff like 0.000000001 units - you don't want to have very large or very small numeric values like that.

But if it helps you to avoid using smaller or larger numbers to use a particular unit system then by all means do that.

- Michael

Ah yes :)
I have confused scale and unities