Size: Diameter: Approx. 0.3 inches (8 mm) (± 1 mm), Inner Circumference: Approx. 6.3 inches (160 mm) (± 0.2 inches (5 mm)). *There may be a deviation of ±0.04 inches (±Please acknowledge The "Kerama Marin" is a new version of the "Kerama Marin" that is inspired by the beautiful sea that spreads around the Keiramama Islands. Firefly glass is a perforated glass ball made using a molding technique called burner work, just like dragonballs The artisan melts colored glass one by one, rolled it into iron core, and layered with silver foil (ginpaku) in a special technique to create beautiful colors. This is not a glow-in-the-dark type that glows in the dark.