100pc Antiqued Bronze Assorted Size 4mm - 20mm Open Jump Rings Jewelry Findin... Quantity: 100 Piece Size: about 4~20mm in diameter, about 0.6~1.5mm thick Iron Jumprings are a basic component in jewelry making and design. It is popularly used as a connector in jewelry construction. It can be used for attaching charms to necklaces or bracelets.