Theese are sea shells loosely modeled from the typical Camino sea shell worn by pilgrims on "El Camino de Santiago de Compostela" also called "El Camino Frances" or "The Way of Sct James" in English. You can order them in 6 different colors. In Spanish a sea shell is called "Concha" (and earring is called pendiente).
The diameter of the holes for ear ring hooks are 1.4 mm - hooks from Shapeways are included (same kind as on the rendering, but different from the hooks on the picture). The with and height of one shell is approx 2.5x2.2 cm (the width and height given to the right, under "Size and price" is for two shells next to eachother).
I also have a matching necklace available in the shop.