In the days before electricity, light below a vessel's deck was limited to candles, oil and kerosene lamps. A clever solution for the light problem was the deck prism. Laid flush into the deck, the prism point drew light down below decks. This prism is a smaller reproduction of Mystic Seaport's last remaining original Charles W. Morgan deck prism. Size: 2.5in x 2.5in x 2.5in For a gift, award, or decoration. Color is Light blue or Turquoise but the color you see in the photo is what I call light blue. Some people call it turquoise. 6 sided pyramid shape.