It's 9.8-10.1mm. 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. ☆ Energy of Amethyst ☆ Protective effect Inner peace Strengthening intuition Enhancing creativity ☆ Recommended for those who ☆ Seek inner peace Need creative inspiration Want to relieve anxiety Want to cultivate intuition ※ If you wish to purchase multiple items, we will offer a discount of 100 yen per item from the second item onwards. ※ 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.