These are stencils for common sizes of round and oval cabochons.

Cabochons are shaped and polished stones prepared for display or to be set in jewelry. They are typically prepared by roughly cutting a stone to shape, tracing or drawing the desired shape onto the stone, and grinding away material to shape and polish the stone according to that outline. These stencils are meant to be used in that process, for tracing standardized shapes onto the stones.

The numbers are the dimensions of the rounds or ovals in millimeters.

You can edit the .scad file or use Customizer to add text to one end of the stencil, such as your name or a company name. The stencils pictured were made for Westcoast Mining (http://www.wcmining.com/).

The prints in the picture were made with ProtoParadigm Citrene and Aquamarine Gemstone PLA.