1. Blackboard protractor, semi-circular
2. 180°, Ø500mm or 250mm Radius, 12.7 mm thick kiln-dried hard wood, w/ 100mm metal handle
3. Angular graduations are in degrees, from 0° to 180°, reading clockwise.
4. Wood Surface Finish: Well-polished and varnished
5. The surfaces and edges must be smooth. There must be no sharp edges.
6. It must be horizontally level when laid flat on a table. There must be no warping.