A great gift for musician out there. Alto Clef is made by it own unique craftmanship. Base Material: Sterling Silver Size: 4mm X 6mm (Approximately) Thickness:1mm Stud Earring comes a long with extra plastic back pusher and a nice jewelry box. This item are Nickel and Cadmium free. Care Guide: When you’re not wearing your sterling silver jewelry, be sure to keep it in a ziplock or airtight baggie as this will prevent moisture from oxidizing it. You can use a silver polishing cloth to remove oxidation from silver and cleaning it right away will make it easier to restore the shine.