50 New 4.5mm 12k Gold Filled Open Jump Rings. This is a set of 50 12 karat gold filled round unsoldered open jump rings. These are for connecting jewelry parts such as clasps, charms, links, etc. Jewelry that is gold filled has gold content equal to 1/20th or more of the total weight of the metal in the piece. Each measures 4.5 mm (3/16") in diameter.