A1587 40-Watt Aqua-Glo Fluorescent Bulb, 48-Inch T8 25-millimeter diameter bulb fits standard and electric ballasts Ideal spectral peaks for enhancing fish color; Promotes plant growth Close placement to water surface offers the potential to maximize light entry into the aquarium High CRI values for accurate viewing of aquarium; Low heat production Perfect for all standard and electrical ballasts; Energy efficient