# CAD Guides: STEP Measurement, Weight & File Formats — Page 5

Practical notes on CAD formats, model properties, units and engineering handoffs. — Page 5

- [STL Volume Zero or Missing? Check the Mesh Is Closed](https://www.cadprops.com/guides/why-stl-volume-is-zero/index.md): Diagnose STL files with zero, missing or unreliable volume by checking watertightness, inconsistent faces, units and export quality before calculating mass.
- [CAD Versions vs Revisions: Track Models and Exports](https://www.cadprops.com/guides/cad-versions-vs-revisions/index.md): Keep upload history, engineering revision labels and converted files separate so a new export does not masquerade as a design change.
- [Compare CAD Revisions: Geometry and Property Checks](https://www.cadprops.com/guides/compare-cad-revisions/index.md): Use fixed versions, explicit units and a deliberate alignment method before interpreting overlays or property differences.
- [Share a Fixed CAD Revision: File and Version Checklist](https://www.cadprops.com/guides/share-fixed-cad-version/index.md): Pin a shared model or comparison to an explicit version, check recipient permissions and handle replacements without silent updates.

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