M2.1 3D models must be supplied in both 'step' and 'wrl' formats
Any 3D model contribution to the KiCad library must be made in both step and wrl format.
WRL files contain material properties and are used for realistic rendering. However they cannot be exported to MCAD packages.
STEP files are used for integration with MCAD software packages. These files do not contain material properties and cannot be used for realistic rendering.