Approximately 10.5mm Inner diameter 16.5~17 It is possible to make the inner diameter smaller. We can do this for an additional 100 yen, so please feel free to comment(^^) As these are natural items, there may be cracks, chips, dents, inclusions (internal inclusions), and variations in color, shape, and size. As the charm of natural stones, We ask that you purchase only if you understand this. Thank you m(_ _)m♡ Cancellations and returns after purchase are not possible. If you are looking for a perfect item, Please refrain from purchasing (＞人＜;) [About the color of the product] The actual color may differ from the image due to the settings of your monitor and the lighting environment. Also, the color of the product may appear different depending on the shooting environment (outdoors, indoors, etc.). [About discounts] * Not applicable for single items or multiple purchases with separate payments. * For bulk purchases, for each additional item after the second item in one transaction, 100 yen will be discounted ^^* Feel free to comment ( *´꒳`*)✨️ (Even if there are comments or negotiations in progress, We will give priority to the person who purchased first. Please understand.)