It is heated with 11 inch flexwatt taped to the bottom controled by a proportional thermostat. The whole bottom is covered with water bottles, then the light difuser sits on top of the botles. It holds 8 egg tubs at once. And yes, with the combination of the proportional thermostat, constant air movement, and water bottles for temperature stability it holds the temperatures EXACTLY where I want them. Temperature is identical in all tubs regardless of location. This is my third year using this incubator.

Just got done putting the eggs in it.