OFFICIAL HARRY POTTER NECKLACE. Harry Potter Charm on a silver plated Necklace. This necklace has been created using the official style guide from Warner Bros. The charm is approx 20mm in height and 16mm wide. The Necklace is a silver plated snake chain which is 16 inches in length with a 2.5 inch extender chain. This necklace comes on the official Harry Potter branded card packaging and shows the Warner Bros logo on the reverse