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