Made of durable styrofoam to help retain warmth and keep a constant temperature. Incubators feature two 4 inch x 8 inch viewing windows - ideal for educational purposes - and solid state thermostat control, thermometer and moisture rings. This deluxe model includes a fully installed circulated air fan it. The Fan Kit improves egg hatching conditions by circulating a constant flow of warm air throughout the incubator. Helps maintain a constant temp of 99.5 degrees F.