Life-Glo Fluorescent Bulb, 15 Watt, 18 Inches T8 25mm diameter bulb fits standard and electric ballasts Closely mimics natural mid-day sun, accurate color rendering Photosynthetic support of plants and corals Energy efficient; High CRI values for accurate viewing of aquarium Recommended for combination with Marine-Glo, Flora-Glo or Aqua-Glo