mine is a 8''x9'' box with 15 w light- note the heat shield on lamp and in a metal bowl. holds heat at 100' just fine I am on day 18. Hatched some in a bigger box last month. I wanted something smaller. cost 16.00 for light,bulb, thermometer.
It is a little water dish. I used it only alittle. when I did open my box to turn the eggs I could feel the moisture in it, plus at lock down I added more. they came out of their shells nice and neat no shrink wrap, or mushy chicks.