... and blue 3. high intensity, smooth surface,more cleansing Luminous Ceramic Pebbles 1.Material: ceramics and photoluminescent pigment.2.Afterglow time ... -4.5cmAverage Weight8g, 20g, 28gShapePebble, Cobble, triangleWater ResistantYesUV ResistantYes Luminous Ceramic Pebbles