After cultured pearls are harvested they are sorted by size and quality. The best quality pearls, that is, pearls that are the most perfectly round, with clean surfaces, the best quality nacre, and the sharpest lustre, are set aside to be matched into pairs for use in making earrings. Earring pearls are only drilled half-way to be mounted, thus the term "Half-Drilled" or HD grade pearls.

These special pearls comprise about the top .01% of all AAA quality pearls harvested, and about the top 0.001% of all Freshwater Cultured pearls harvested each year.