Down is a spherical structure of fibers under the calamus that cling and grow onto muscles in the abdomen and hollow under the wing. It is chiefly for maintaining a warm body and radiating. DOWN is only 8-10% of the plumage of a goose or duck. It is a rare and natural warmth keeping material. The densely covered thousands of tiny air holes on the spherical structure absorb human body heat, cut off outside cold air to provide the best protection against the cold. Feathers are light, gentle and with good elasticity. Among natural materials, we may say feathers are the most ideal filling material for clothing and quilting.