20mm calibration dice

I'm printing so many of these cubes testing new filaments, print beds, extruders, nozzles... so blank ones and ones with XYZ are nice for testing but fairly useless for anything else so I made a small change and added 1-6 markings on a 20mm cube so I can use them for a game (give them away to ppl to use for games).. they are not "balanced" of course and depending on your infill settings will prefer some numbers but still better then xyz ones :D

**20181003 UPDATE:** trough comments (thanks jst