6mm is the inner diameter of the hoop. This 18g 6mm hinged ring hoop is VERY SMALL! We don't suggest male customers and the persons who have big nose or ears to pick this size. If you never wore 6mm before, try to pick larger inner diameter. This ring's size info: 18 gauge (thickness: 1.0mm), inner diameter 6mm ( 15/64 inches ). Small surgical steel earring hoop: 316L surgical steel, polished very well, comfortable to wear without sharp edge. Sold individually. It can be used as cute nose rings for nostril piercing for SMALL nose of WOMEN (piercing is closer to the edge), helix earring hoop, forward helix earring, rook earrings, snug earrings, daith earrings, tragus earrings hoop, anti-tragus earrings, cartilage earring hoop and second or third lobe piercing hoop for small ears. Save time - easy to open and close the click closure by hand, Not require a tool.And it's still tight after long-term use, needn't to worry about lost when bathing, walking or exercising. 18g Nose Rings 6mm Cartilage Earring Hoop Surgical Steel 18 Gauge 18k Gold-plated Nose Hoop Tragus Daith Helix Rook Piercing Jewelry