These are rectangular earrings with wood-grain cut out of the surface. While these were originally designed for SLS/DLP/SLA printing they will actually print perfectly on an FDM machine, as long as you print the model on an edge. If you print them flat with an FDM machine they will NOT come out nearly as nice and will likely have gaps/holes.
They Heavy Grain model is designed to be painted. The grooves can be filled with paint to make a 2 color earring.
The Subtle Grain model is designed to be printed as one color and not painted.