Exo Terra Bulb 200 No longer should anyone rely on the old 5.0 and 10.0 UVB principle, as these fictive numbers only vaguely indicate the UVB output of the bulb ranging between 280-320nm. The wavelength that is responsible for vitamin D3 photosynthesis however, ranges from 290 to 310 nm with a peak production at 294nm. The UVB range below 290nm is undesirable, and can even be harmful, while radiation above 310nm destroys vitamin D3. The positive effects of UVB lighting for your reptile also depend on many other factors, such as whether the bulbs are correctly sited, changed regularly and turned on for a sufficient number of hours. The Exo Terra Reptile UVB200 emits the ideal UVB spectrum for optimal Vitamin D3 photosynthesis. The Reptile UVB200 Bulb is especially xto simulate conditions for reptiles with very high UV requirements, like diurnal reptiles from desert environments. These areas receive direct unfiltered sunlight with high levels of UVB. The significantly high Vitamin D3 yield index results in increased vitamin D3 photosynthesis to aid calcium absorption and prevent metabolic diseases. The extended UVB penetration makes this bulb the ideal choice for taller terrariums or terrariums with denser screens. Ideal for desert reptiles with very high UV requirements. UVB helps prevent metabolic bone disease. Ideal for desert set-ups or taller terrariums. Very high D3 Yield Index. Increased Vitamin D3 photosynthesis. Maximises calcium absorption. Enhanced UVB penetration distance.