(3 Pack) Zilla Incandescent Bulb, Day White Light & Heat, 75 Watt. Day White Light Incandescent Bulbs. Provides basking heat source for reptiles to regulate their body temperature. Simulates the natural daytime photo-environment of the reptile's habitat. The bulb simulates the natural daytime photo-environment of a desert or tropical habitat while providing a heat source needed for a healthy reptile environment. Photons from the daylight bulb pass through the glass heating the opposing surface allowing the reptile to bask in its warmth. The bulb is made from glass containing rare earth neodymium phosphors to produce a brighter, whiter light.