Beautiful large freshwater pearl with Sterling silver CZ setting. The pendant top is an enhancer, meaning the top ring opens to attach on the necklace. There is also a safty latch to secure the ring when it's on the necklace. Inside diameter is 7 mm, just a bit over 1/4 inches. 
 
From the top to the bottom of the pendant, it is 1  5/8 inches. Black rubber cord, 18 inches.