Conversion from U3D to CATPart is not supported yet :(

Universal 3D (U3D) is a compressed file format standard for 3D computer graphics data.

The format was defined by a special consortium called 3D Industry Forum that brought together a diverse group of companies and organizations, including Intel, Boeing, HP, Adobe Systems, Bentley Systems, Right Hemisphere and others whose main focus had been the promotional development of 3D graphics for use in various industries, specifically at this time manufacturing as well as construction and industrial plant design. The format was later standardized by Ecma International in August 2005 as ECMA-363.

The goal is a universal standard for three-dimensional data of all kinds, to facilitate data exchange. The consortium promoted also the development of an open source library for facilitating the adoption of the format.

CATPart is a native format developed by Dassault Systems for storing parts of the assemblies created in CATIA V5 software suite, which is extensively used in mechanical engineering including aerospace, automotive, shipbuilding and other domains.

CATPart stores geometry, structure and metadata of 3D models dedicated to single parts. Multiple CATPART files can be combined into a CATProduct assembly file.

Among CAD applications that support CATPart extension are Autodesk Inventor, Fusion 360, and 3ds Max.