Fluker's incandescent light bulbs provide the radiant heat (infrared light) that reptiles need. Reptiles are ectothermic and depend on their environmental temperature to regulate their core body temperature. If a reptile is not provided an appropriate environmental temperature range (ETR), it may be predisposed to chronic infections,. Because ETR's vary from species to species, ask your pet professional or review available literature for guidance in determining the appropriate ETR for your pet. Fluker's has provided an easy-to-read reference table to simplify bulb selection based on the distance the bulb will be placed from the reptile.