Zoo Med Powersun UVB Mercury Vapor LampZoo Med PowerSun UV is a self ballasted mercury vapor bulb with two main components. The first is a standard incandescent filament, which is the first to light. Provides essential UVA, UVB light and heat all in one lamp Self Ballasted mercury vapor UVB bulb Keeps your reptiles healthy by preventing metabolic bone disease The second is a mercury vapor arc tube, which takes a few minutes to heat up. There will be a noticeable change in hue (or color)