This Is designed to fit the 12 cubed printer to colorize natural or white filament. Use crayola markers or permanent markers. It has support in the file. You may need to clean the holes for fit. I am working on getting it dial in perfectly but works ok for now.
print a a slow speed high res. After printing remove center support. clean to pen size. You might have to run a 2mm or 1/8" drill in the center hole for clean running filament. insert up to 4 pens and have fun