Unlike traditional ballasts, the electronic ballasts of the Exo Terra Linear Top prevent flickering to reduce stress in reptiles and amphibians. Optional accessories such as the Exo Terra Digital Thermometer, Hygrometer or Combometer can be slid into the special sliding rim on the top of the canopy. Holds 2 linear fluorescent tubes. Ideal to combine ultraviolet and visual light spectrums. Reflector increases light and UV output by up to 100%. Individual On/Off switch. With electronic ballast. No flickering; less stressful for reptiles and amphibians. Sliding rim to mount accessories.