This Item replaces PT2171 20w Repti Glo 10.0 Ideal for all desert dwelling reptiles High UVB output Very high D3 conversion Provides necessary UVB rays for optimal calcium metabolism Recommended for terrariums with dense screen covers 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. The longer sizes can be placed on multiple terrariums. The packaging includes all necessary information: Full Spectral Graph, UV Spectral Graph, Reptile Bulb Rating System and distance related information like: UVB output - Photosynthesis - Ferguson Zones and Exo Terra Reptile UVB Chart.