Magic Metal DNA Double Helix Necklace Antique Silver Tone Genetic Molecule Structure Pendant NQ69 Fashion Jewelry Ships from the USA DNA Double Helix Necklace. 3D Molecular structure necklace. Pendant Length: 1.25 inches. Length of Chain, Open from Clasp to End: 20.5 inches Makes a perfect gift. Search Magic Metal Jewelry for more jewelry styles.