i made mine from a redundant fridge,,removed the gubbins from the back. steam cleaned it and fixed two inline bulb holders on the bottom,with two trays in , the top ones for eggs and the other is where i place the water trays,it has a dimming thermostatic device £40.00 and it holds temps to within .3 of a degree, on top of that i also use a small hygrometer placed near the vision panel i cut out of the door, about 12 x 9 inches .incidently i found using a algae cleaner for an aquarium is great for demisting the window. the thermostat just has a probe i leave in the middle of a wire basket tray linedd with triple kitchen towel for resting eggs on,