These 1/2 inch diameter cobalt blue hoop earrings are wonderful. They are made from 100% niobium wire that has been anodized to create this beautiful cobalt blue coloring. Since the metal is anodized, the color will not wash away. The metal is permanently colored with this cobalt blue coloring. Niobium is considered to be a hypo-allergenic metal by the American Academy of Dermatology. http://web.archive.org/web/20150326032045/https://www.aad.org/media-resources/stats-and-facts/prevention-and-care/tattoos-and-body-piercings Reverse hoops are a little different than most hoops. These niobium hoops are designed to be clasp-less. They are worn by inserting the hoop earrings into the back of your earlobe and gently tugging it forward. Each hoop has a catch on the back of the hoop to stop the hoop from going all the way through your piercing. These elegant thin hoops are lightweight and designed for a standard piercing. This means they will not tear or stretch your earring holes.