Equal to a 350 Watt incandescent bulb, the 6400K bulbs are great for a vegetative grow room. These bulbs are used and have about 3 months of 18 hours per day usage. They are still bright and strong and will easily go for another few years. I'm just not growing anymore. Normally about $35 each new. Standard lightbulb socket. Very large and very bright. They run much cooler than regular or high intensity bulbs like HPS.