1x 55W OSRAM Dimmable 2GX13 4 Pin, T5 Round, 300mm Circular Light Bulb. 2GX13 4 Pin Base, Colour 4000K. 8,000 hours average lifespan; 4000K cool white. Being almost circular, they are a great alternative to linear fluorescent tubes; compact, bright, they provide a good all-around light.
eBay