The Reptisun 5.0 and Iguana Light 5.0 both have the highest level of both UVB and UVA wavelengths (according to independent laboratory spectral analysis.) UVB wavelength helps to prevent or reverse Metabolic Bone Disease in Green Iguanas as well as other species of lizards in captivity. Strengthens and improves shell growth on all captive turtles and tortoises. UVA wavelegth increases appetite, activity, and helps to induce reproductive behavior in captive reptiles. Safer than adding powdered or liquid synthetic D3 supplements, as the UVB wavelength allows all reptiles the ability to regulate their own Vitamin D levels by endogenous synthesis as they would in nature. Eliminates risk of vitamin D3 overdose (highly toxic) from synthetic sources. Wavelength penetrates a full 10-12" from bulb's surface. Bulbs last a minimum of one year before diminishing wavelength. (Replace Bulb at 1 to 1 1/2 years.) Spectral power distribution studies show that tungsten filament bulbs (Neodymium bulbs or spot lamps) do not emit UVB and therefore do not assist the animals in D3 synthesis or calcium absorption.