Our wool comforters are filled with Pure Grow Wool and covered with soft unbleached natural organic cotton muslin. Wool is the perfect insulating material for a comforter. Air trapped between fibers provides great warmth in winter. Wool warms up to you almost the moment you lay down, responding to your body temperature. Wool also keeps you comfortably insulated and cool in summer. Bedouin tribes in the desert wear wool clothing for this very reason. Wool is comfortable in any season. These comforters insulate your body temperature by wicking moisture away from your body. Porous and permeable, wool absorbs perspiration and releases it slowly through evaporation so that in winter you feel less chilled and in summer you are comfortably cooled. You will not wake up overheated or too cold in the middle of the night.