This is bale to hold an object on for products with flat back 12mm 4 prongs It is 20mm from leading to base, up to 13mm broad, 8mm thick one specified purchases one bail, 3 purchases 3 bales, and many others.
Medium size bail for irregular stones with flat back
Sterling Silver, stamped 925 on the back
20mm top to bottom, up to 8mm thick
Medium size, 4 long prongs, for stones about 12mm