The long tube UVB bulbs are best, like Zoomed's Repsitun model: http://lllreptile.com/store/catalog/reptile-supplies/uvb-fluorescent-lights-mercury-vapor-bulbs/-/zoo-med-24-repti-sun-100-fluorescent-bulb/ Remember to replace UVB bulbs according to the manufacturers recommendation after which time the bulb will no longer produce UVB even if visible light still is.