Under natural conditions, the sun produces ultraviolet B (UVB) radiation. UVB radiation is needed to produce vitamin D. In captivity, reptiles that have poor lighting conditions can develop life-threatening diseases. Sun Glow fluorescent bulbs provide essential ultraviolet B radiation for captive reptiles and amphibians. These Bulbs generate more UVB (> 250 watts/cm) than competitor's 5.0 fluorescent tubes (> 250 watts/cm)! Sun Glow bulbs should be used in combination with Repta-Sun incandescent bulbs which can be used to regulate the environmental temperature.