316L Stainless Steel, also known as "Surgical Steel", is approved by the Medical as a non-toxic and harmless metal that is highly resistant to radiation and corrosion. It's also called as "Space Metal" since it was once used only in the astronautics. 100% genuine gold, IP vacuum furnace Plating instead of superficial plating makes the 5mm gold and titanium combine perfectly. The allergy rate is as low as that of 925 sterling silver, the few allergic persons can wear them after the auricular needle is wipped with alcohol. Please confirm the material before purchase as alloy would fade in just a few weeks while 316L Stainless Steel's color would stay forever.