This is a Ring Generator. It generates rings with embossed 2D shapes according to the parameters given. The embossed shape can be given by a unit-sized and centred dxf file.

To generate your own personalized ring you need the MetaCAD AoI plugin - which is still in beta mode. If this does not scare you the plugin can be found here: http://objects.reprap.org/mediawiki/index.php?title=Builders/Metalab/AoI_MetaCAD

For all the others I included two generated STL files of rings with:

24mm inner diameter 1mm wall width 7mm height

in two variants: One has stars the other hearts embossed on the outside.

I also uploaded the star dxf file that parametrized the heart ring :)