The GLO T8, 20W Double-Bulb Electronic Ballast Fluorescent Lighting System provides flexible lighting solutions for aquarium cabinets, multiple aquarium setups on store racking, shop set-ups and custom installations. This convenient, practical, well-equipped, aesthetically-designed lighting system includes everything you need to make your installation simple and adaptable to most applications: - Electronic ballast technology for low-heat, high-energy efficiency - Easy-mount ballast housing - Ample electrical wiring for series placement of bulbs in multiple aquarium rack-type set-ups - Water resistant end caps - Adapters and bulb clips for T8, T10, T12 applications - Illuminated On/Off switch The lighting system is easy to install: simply mount the ballast and bulb clip holders to a solid surface and attach the water resistant bulb end caps to the bulb and you are ready to light up your aquarium installation. Bulb size: 61cm (24").