The Exo Terra Reptile UVB100 emits optimal levels of UVB, similar to that of shady environments such as rain forests or other tropical locations. Reptiles living in these habitats receive moderate UV radiation due to climatological conditions (fairly high humidity, changes in weather, etc) that prevent unfiltered sunlight from reaching the reptile’s basking site. The optimal Vitamin D3 yield index ensures vitamin D3 photosynthesis to aid calcium absorption and prevent metabolic diseases. Light and UV radiation in compact fluorescent bulbs decreases over time. Changing your terrarium bulbs yearly ensures optimal light conditions to keep your reptiles healthy. Visit www.exo-terra.com and register for the “Restore The Rays” program and be reminded when to replace your bulb. Pet care bulb for use with Reptiles, Amphibians and Invertebrates only!