For easy incubation, use the Yogotherm when making yogurt, kefir, acidophilus milk, fresh cream, etc. Yogotherm consists of a 2-liter high-density polyethylene inner container (BPA-free) surrounded by polystyrene insulation. The insulation is protected by a hard plastic outer shell and lid. The Yogotherm will maintain incubation temperature within a few degrees of the original temperature. No electricity required, very easy to use and clean. Up to 1/2 gallon (2 liters) capacity. Removable parts; replacement/extra pails available.