FC12T9/CW is a widely used 32-watt, 12-inch circular (circline) fluorescent tube light bulb commonly installed in ceiling fans, kitchens, closets, and garages. The coding breaks down to FC for Fluorescent Circular, 12 for the nominal outer diameter in inches, T9 for the tube thickness (9/8ths of an inch), and CW for the Cool White color spectrum.