One that the operater pays close attention to. There are no incubatprs that just haych the eggs for you. Even when I was hatch commerically, up to 10,000 chicks in one week, we had to pay attention. Now I use a number of the cheapest ones on the market, L G's with a very good hatch rate. It is like saying, I have a BMW so I am a better driver than you, for you omly have a Chevy.