(Smucker Mfg) The Roy-L-Heat Animal Warmer helps you save hypothermic calves and lambs, plain and simple. Every calf or lamb dropped in the bitter cold of winter stands a chance of losing valuable body heat. You stand a chance of losing those newborns, and the income they represent. The box is made of tough, high-density polyethylene. Its interior size provides adequate space for calves to lie down and to stand up. Opposite the heater is a rubber "head boot" which permits the animal to breathe outside air when desired, yet holds the warm air in at all times. The "attic vent" allows excess moisture to escape.