Diameter calibration ring

Nothing fancy here.
I needed a model to test/calibrate the inner diameter my printer was producing.
This is exported from Autodesk Fusion 360 with a "_High Refinement_" setting so the circle is more precise.

1. One _small_ ring **15mm outside** diameter and **10mm inside** diameter. **3mm height**.
2. One _large_ ring **30mm outside** diameter and **20mm inside** diameter. **5mm height**.