The base inner diameter is 16. Size adjustments are only possible for sizes 13-16. For sizes larger than 16, please confirm if it's possible before purchasing m(_ _)m Cherry Blossom Agate 9mm Rose Quartz 9mm Videos are posted on Instagram ▶︎ ichigohime__ Please read the profile before purchasing. We do not accommodate metal allergies, but if we have the stone in stock, we may be able to remake the item without metal parts, so please check before purchasing ( ´._.`) As these are completely handmade, we appreciate your understanding. ※ Please check the images carefully and make your own judgment. If you have any questions or concerns, please ask before purchasing. We do not accept returns, refunds, or exchanges after arrival. I am a handmade seller! Please understand. If you are looking for perfection, please purchase from a shop. (※) The price includes shipping, packaging, and handling fees. (※) Please leave a comment if you would like a discount or a discount for multiple purchases m(_ _)m Requests without a comment will be rejected. Please also read the profile (♡ᴗ͈ˬᴗ͈) We do not accept custom orders, only size adjustments.