Internal diameter = 12mm, external diameter 16mm, these strong, surgical steel hoops would suit older girls through to adulthood. Also available in 10/14mm for children to perhaps age 10. A pair for Mum and a matching pair for daughter? What is IP Gold? "To begin with, a layer of titanium nitride is added to the base surface of stainless steel. Additionally a final plating metal is added to the surface; the thickness of this layer is no more than 0.3 urn. ... Given its durability and chemical stability, ion plating is rightly called “permanent” coating."