Mini round bubble level tool in metal shell (has 3 screw holes). Number of pieces in this set: 5
This is what you need if you are making your own level tool or something similar. The bubble indicates if something is level in all horizontal directions. These spirit levels are often used with (sail)boats. Of course you can glue this tool to any object that you want to be level.
Height: 10 mm, diameter: 22 mm, diameter screw holes: 2 mm (see photo 2)