Fossil Coral Size: Approximately 10mm Inner Diameter: Seems to be larger than 16mm. I'm not sure exactly because there are no other sizes. Unused Please refrain from purchasing if you are concerned or seeking perfection, as this item is stored at home and inspected. This item is available for combined purchase requests. 100 yen off if you purchase two items together. 200 yen off if you purchase three items. *Please note that the color of the product may appear slightly different from the actual color in the photos. *As this is a natural product, there may be cracks, chips, black spots, color unevenness, scratches, etc. Please understand this beforehand before purchasing. It will be placed in a zipper bag and wrapped in bubble wrap for shipping. *This listing may be stopped or disappear. This is because it may be sold elsewhere, or if it is sold, please understand.