The UVB wavelength helps to prevent or reverse metabolic bone disease in green iguanas as well as other species of lizards in captivity as well as strengthens and improves shell growth on all captive turtles and tortoises. UVB wavelength increases appetite physical activity helps to induce reproductive behaviors and is beneficial to the psychological well-being of captive reptiles and amphibians safer than adding powdered or liquid synthetic d3 supplements as the UVB wavelength allows all reptiles the ability to regulate their own vitamin d3 levels by endogenous synthesis as they would in nature wavelength penetrates a full 20 in from the bulb s surface pure quartz glass sleeves the bulb s UVA/UVB wavelength