Ohta Yoai Ceramic Coasters Set of 6 Diameter: approx. 8.7cm The hellebore coasters have small black dots from when they were purchased. Please check the 3rd image. The surface is ceramic, but the back is cork, so they are easy to use and less likely to scratch tables. I liked the design so much that I sometimes displayed them on a shelf, but they were mostly stored in a dark place. They have not been used as coasters, so I believe they are mostly clean, but please examine the images carefully before considering to avoid any issues. Botanical Art Plant Painting Ohta Yoai Watercolor Painting y.ohta Coasters TOKO JAPAN Ceramics Y.Ohta Botanical Art Collection