Create in Comfort. The OttLite 508 Illumination 13-Watt replacement tube (electronic ballast) delivers the right mix of brightness and contrast to bring true colors and comfortable clarity to your world so you can enjoy your time even more. You'll see colors accurately so you can make selections with total confidence. And, you'll see fine print and details with ease under this unique low heat, low glare illumination that helps reduce eyestrain. The output of a 13-Watt OttLite tube is roughly equivalent to that of a 60-Watt incandescent bulb. So, they use about 1/4 the amount of energy for the same amount of light. However, it's not just about energy-savings, it's also about the quality of the light. Click Here to learn more. PLEASE NOTE: This tube has an electronic ballast and is designed to work only with certain OttLite lamps. This bulb has a single ridge and is for an E-type ballast. If you are trying to replace a current bulb, check and see if the fixture was made after January 2008. If it was after 2008, has an E on it, and your fixture takes an electronic ballast, than this bulb will work. However, if you are looking for a bulb to replace one with double ridges on the base with an magnetic ballast, than a bulb type A is what will work. Failure to purchase the correct tube may affect the durability and performance of your purchase. For use only F48, 783003 and KCY008 lights purchased after January 2008. Model T13330A needs to be used for lamps purchased prior to January 2008.