the belly heat option for animal plastics is a heat cable. it is heavy gage wire recesed into a routed cut out on the under side of the cage floor. it covers 1/2 of the cage. i am useing a johnsons controls a419 abc thromostat. the room or house temp is set to 70 during the winter. the heat cable is more than capable of heating the cage even higher. than the 89-92 range i have it set for. dont let your house temps fall below 70 or you will have to run a second heat sorce to get the cool side up.