The Exo Terra Reptile UVB150 has a very high UVB output similar to sunlight in deserts. These locations receive more direct sunlight, therefore desert reptiles are more exposed to UV radiation than any other type of reptile. This bulb can also be used on terrariums with denser screen covers to ensure sufficient UVB penetration. Dense screens can filter out up to 50% of the UVB rays. The high 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!