Niobium is a hypoallergenic refractory metal. These are a gray color and can be substituted on any of the silver-tone earrings. If you would like your earrings made with hypoallergenic niobium earwires, select the niobium earwire from the selection box when you add your earrings to the cart. If your niobium earwire isn't featured in your earrings' selection box enclose a note (in the comments box) telling me which niobium hooks you'd like on which pair of earrings in your order.
There is no additional charge for substituting niobium hooks on your earrings.