15x13mm Brass Connector-Settings

Price listed is for two connects. These are approximately 15mm by 13mm brass connectors. They have a scrolled leaf design and three loops. They have a recess on the back that has prongs, which I believe is to hold a stone. I am not exactly sure what kind of stone is suppose to fit in these. The recess measures about 9x5mm. They should hold a baguette or an octagon. At 10/5 baguette and a 10/5 octagon were too large. I tried an 8/4 octagon and it works but, seems a little small for these. If you could find a stone that is 9/5mm it would probably be perfect. The measurement includes the loop