It's 9.6-9.8mm. Inner circumference is 16cm. Adjusting the inner circumference smaller is free, but increasing it to 17cm costs an additional 100 yen, and 18cm costs an additional 200 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 discount each item after the second one by 100 yen. ※ Immediate purchase is OK ^o^ We will prioritize those who purchase immediately, even if comments are in progress. ※ There may be inclusions and dents unique to natural stones. Please understand this as a characteristic of natural stones.