If you are a fan of the vintage West German glass like I am, you will love this clasp. The blue opal glass is charming, with hints of gold and the swirls of color that make opals so beautiful. If you are like my Grandmother, who believed that to wear an opal if it isn't you birthstone is bad luck, you can wear this! It only looks like an opal. The centerpiece is 10 mm by 12 mm and is set in a handmade sterling silver box clasp. The clasp is 27 mm from ring to ring.