The Exo Terra Reptile UVB 150 is a 13-watt compact fluorescent bulb that produces UVB light for desert reptiles kept in terrariums. Reptiles use UVB to make vitamin D3, which helps them use dietary calcium. Mount it in a suitable fixture or canopy, run it on a regular day cycle, and replace it on the schedule the manufacturer recommends, since UVB output fades before the visible light does.