Small Square Synthetic Opal Stud Earrings Vintage Antique Style Stering Silver 925 Posts Studs (E23680) Part Size : 6 x 6 mm. / Opal: Stone size : 4 mm x 4 mm. Material - genuine 925 sterling silver. Nickel and Lead free. Conform to International, European an American legislation regarding lead, nickel and heavy metal content. Finishing: Oxidized + E-coat Gift Box available