ALZO 27W CFL Photo Light Bulb 5500K, 1300 Lumens, 120V, Pack of 4, Daylight White Light 27W CFL photo bulbs with daylight color temperature of 5500K, 120V, CRI of 91; pack of 4 Brightness of 1300 Lumens at 1m, flicker-free; renders colors accurately for photography This is a large bulb that might not fit standard household lamps, see diagram above; fits all medium-base E27/E26 sockets Dimensions: Length: 6.5 inches; diameter: 2.5 inches; energy-saving bulb with about 10,000 hours life Important: ALZO CFL bulb life is based on the bulb in an open air fixture with sufficient ventilation; when ALZO bulbs are installed in fixtures that lack adequate ventilation, the life of the bulb will be greatly reduced.