MagneticCopper Bracelets are made of Pure copper, not brass, not alloy, not stainless steel. Copper is a red metal, also a green metal. After a long time in the humid air, the copper surface will form a layer of patina slowly, this is oxidation. So your bracelet turns green, it's normal and proves that the bracelet is made of pure copper.Suggest you take it off when you are swimming, taking a shower, or sweating for a long time, avoid the bracelet becoming green due to prolonged exposure to seawater, sweat, or salt water. If it turns green, please don't worry,Tips: Our Copper Bracelets were coated. The best way to check if a copper bracelet is made of pure copper is to cut the bracelet and check inside is copper color.Warning!! Do not use this product if you have a pacemaker, defibrillator, insulin pump, or any other implantable electronic medical device, or if you are pregnant.