This is a great 3D STEP(.stp or .step format) model viewer. STEP format (ISO 10303) is an ISO standard for 3D data exchange. It is widely supported by almost all 3D CAD, CAM, CAE, PLM applications including CATIA, Autodesk Inventor, SolidWorks, NX, ProE (PTC Creo, ProEngineer), etc. With help ...