This drop has 1 soldered closed 4mm jump ring at the top.
Inside diameter of jump rings 2mm.
Most stones Plazko.com sells (in chains, charms, connectors, drops, or other products) are enhanced to globally acceptable standards. Stones are commonly enhanced to improve their color, clarity, and durability. There are many ways stones are enhanced. Some of the common enhancements are irradiation, heat treatment, vapor deposition, dyeing, filling, and impregnation.