Conversion from U3D to PRT 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.

A PRT format is used to store components of 3D CAD models. It may contain lines, surfaces, textures, dimensions, and metadata.

The .prt extension is mostly associated with the Siemens NX Part (PRT) file type as an acronym for "part". PRT files may be exported to various standard CAD and 3D modeling formats (e.g. OBJ and STL) in addition to being utilized natively in Siemens NX.

The PRT file is also a part created by PTC Creo Parametric 3D software. In PTC Creo, project part files can be combined in a single assembly file with an ASM extension.

Despite the same extension name different CAD software produce PRT files differently, i.e. PRT files produced with Creo are not the same as PRT files generated from NX.

The PRT extension is also compatible with Dassault Systèmes SOLIDWORKS.