I got this replacement bulb for an older OttLite. It was the bulb that was supposed to fit, but I couldn't get it in. I've replaced bulbs in other OttLites with no trouble. OttLlite customer service was no help at all. They wanted me to call them M-F between 8:30 and 5:30 so they could walk me thru what I had to do to make the bulb fit. Um, I work then and why don't they just make a bulb that really fits? They don't work any extended hours. My husband finally got the bulb to fit by modifying the lamp. Don't get this bulb and think it will automatically fit and don't expect a lot of help from OttLite. Email customer service doesn't do a thing except tell you to call at their very inconvenient hours. I think OttLite has had the market cornered for too long. I'll be looking for something else when my Ott fixtures go bad.