It's 9.2-9.3mm. Inner circumference is 17cm. Adjusting the inner circumference smaller is free, but it can be changed to 18cm for an additional 100 yen. ☆ Rose Quartz Energy ☆ Heals the self Reduces stress Balances oneself and others Heals childhood emotional wounds Allows you to be kind to yourself ※ If you wish to purchase multiple items, we will offer a discount of 100 yen for each item after the second one. ※ Immediate purchase is OK ^o^ We will prioritize those who purchase immediately, even if there are comments in progress. ※ There may be inclusions and dents unique to natural stones. Please understand this as a characteristic of natural stones.