Built directly into Revit (walls, floors, roofs, ducts, pipes). These are not external files but are native to the project environment. You cannot save a single wall as a standalone .rfa file.
Loading high-polygon objects (common in manufacturer libraries downloaded for free online) can destroy model performance. A sofa with 100,000 polygons might look great in a render but will slow down navigation to a crawl. bim objects for revit
