Compact fluorescents give off UVA and UVB rays besides normal light. UVA is needed to stimulate feeding, digestion and reproduction in diurnal reptiles which can see UVA and normal light spectrum. The addition of UVA means that the environment looks like their natural habitat. UVB is used by diurnal reptiles to promote Vitamin D3 synthesis and helps prevent or reverse metabolic bone disease in captive reptiles. These lamps give off 5% UVB and are rated 26W. Ideal for tropical and other medium UVB requirement reptiles, including Tortoises, Monitors, Bearded Dragons, etc. To maximise output into a vivarium we recommend using a silver aluminium clamp lamp or our over head compact lamp holders. When placed in a reflector the maximum amount of light enters the vivarium and creates a highly concentrated and localised UVB/UVA area, an absolute must for all day active reptiles and amphibians. These are screw fitting (ES E27) and have built in ballasts. It is recommended that UV lights are replaced every year to maintain high UV output.