Thank you for viewing. Material: Natural stone, high-cost-performance black aquamarine. A must-have for aquamarine lovers! It's a very beautiful stone, and the minerals inside the stone are clear, so I think you'll be very satisfied at this price. Aquamarine prices have doubled since last month. They say it will go up even more from now on. Please collect it while you can. This class of stone would cost over 20,000 yen at stone shops in Japan. Size: Inner diameter approximately 18 cm As it is a natural stone, there may be natural cracks and color unevenness. Also, it is tied with silicone rubber, so please be able to repair it yourself if it breaks. It is very fragile, so please refrain from dropping it or handling it roughly. Please also remove it when exercising. We can also repair it, but shipping and repair fees will apply. We will take a video during packing, so we cannot accept claims for damage. Please be sure to take a video when opening the package. Due to the above reasons, we cannot accept returns or claims, so please understand.