The set is made of 14K solid yellow gold. Each is hallmarked 14K inside. They measure 11.7mm (just under 1/2") in diameter x 3.75mm in width. 2nd pic shows how small when sitting on a dime. In any light the lab created opals show green, blue and pink color. Set weight is 1.8g. They are new, old stock I've had for 17 years. They have never been worn and are in very good condition.