This connector has 2 soldered closed 4mm jump rings at top corners.
Inside diameter of jump rings 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.