These are blank label plates for the Multiboard system by Keep Making. Add text in tinkercad, your slicer, or your favorite 3d modeling software or keep it simple with a label maker. These are 50, 75, and 100mm.

These are printed face down with 3 walls, a 0.2 layer height, and 15% infill. You can add a contrasting color by inserting a couple pauses in your slicing software and changing the color of filament.