Authentic Murano Glass Disc (lentil), we call them windows because an interior spiral of filigrana wrapped around .925 sterling silver foil can be seen through the outer layer of clear transparent Murano Glass. This maximum usage of clear Murano glass gives this bead a great look. The size is approximately 37mm in diameter with a 1mm hole running through the center. The color of the spiral in this one is Black Murano Glass.