These detailed bird earrings have a light 14-karat gold plate on brass. Two magnets hold them on the ear; a plated neodymium magnet in front and a painted ceramic magnet in back for total comfort all day long. I think you will find these to be the most comfortable non-pierced earrings you have ever worn. They are 12 x 15 mm in size and sold as a pair. Need extra or stronger magnet backs? They are listed here: https://laurawilsongal.com/products/extra-magnetic-earring-and-eyeglass-holder-backs If you have misplaced your metric ruler, remember that 13 mm=1/2 inch. Remember: The wider the magnets, the more comfortable the earring is. If you are allergic to nickel, order only earrings that have both enamel painted ceramic magnets front and back since the neodymium magnets are plated with nickel.