BlenderGems is a library of objects that you as designers or jewelry designers can use for your custom items. These add ons work with Blender 2.79 to 2.82 and above. They are all obj files, so if you can import obj files into the cad program you use, they are compatible.
Each of these items has been testes. They will all 3d print.
You can Purchase BlenderGems, and get free updates for 1 year from your purchase date. I update these usually once a month.