This necklace is stunning. It contains Roman glass that comes with a Certificate of Authenticity. The rounded box chain is 18" long and made of Sterling silver. This necklace has an 18 mm x 30 mm oval shape rope design pendant. The pendant features an 11 mm x 19 mm Ancient Roman glass center. The color of Roman glass will vary. Lobster clasp closure on .8 mm rounded box chain. .925 Sterling Silver