Hi Michael T, so I found out what is going on with that second STEP file, the one from SolidWorks - it's actually a bug in MoI and not in the STEP import library itself.

It's possible for STEP files to store not only a unit system but also a scale factor that is supposed to be applied to the unit system as well, and MoI was not paying attention to this additional scale factor.

So for example that file you posted has 1 unit = 1 inch in size, but for whatever reason instead of it just directly saying that the units were inches, it instead was set to say that the units were meters with an additional scale factor of 0.0254 applied to it (which is 1 inch in meters). But MoI was only picking up on the meters setting part and not the additional 0.0254 scale factor part.

So I've added that to my list of stuff to fix in MoI. Thanks for posting the example file,

- Michael