Cool Grow Lamps emit light from 5,500ø K, imitating the natural look of daylight. They are an ideal light source for the seedling and vegetative stages of plant growth, while still emitting a wide spectral distribution. Sunmaster? Cool Metal Halide Lamps surpass many other HID sources in PAR watts?the most objective measurement of total light energy available for photosynthesis. Designed for optimal performance on electronic ballasts.