Zoo Med Repti-Therm Under Tank Heaters are an excellent primary heat source for temperate, terrestrial reptiles and as a secondary heat source for tropical and desert reptiles. The heaters permanently adhere to your terrarium, forming a solid bond for better heat transfer. They contain a solid state nichrome heating element and are UL/CUL approved. Heaters range from 4 to 24 watts and cost almost nothing to operate. Includes rubber feet to slightly elevate your terrarium to allow excess bottom heat to escape.