OnShape uses Parasolid (best-in-class geometry kernel used by a LOT of different commercial CAD products) under the hood so if you are trying to make a manufact

OnShape uses Parasolid (best-in-class geometry kernel used by a LOT of different commercial CAD products) under the hood so if you are trying to make a manufacturing quality part it will stand you in good stead. OpenCASCADE (FreeCAD's kernel) is pretty good too.