Caltar Professional Quality135 Watt 5500k Photography Continuous Day Light Spiral Fluorescent Bulb Professional Studio Lights based on new technology that produces ultra soft light without hard shadows. They are daylight balanced, also known as white balanced, at 5500K Kelvin that makes them easy to be combined with ambient window light. Energy Saving Compact Fluorescent Spiral Bulb Designed for Umbrella Reflector for High Performance