A well-made cold-weather jacket is actually two parts of a cold-weather jacket sewn together - the inside part to protect against the cold and the outside part to block the wind. The inner part uses mainly a nylon lining, then adds the key ingredient: a film to stabilize and protect the insulation, plus a thick layer of polyester warming material. At this point, the thermal layer is larger than the lining - this ensures that every part of the jacket is warm. The outer fabric of the winter jacket is usually made of thick nylon fabric, and the lining is a special fabric with small holes through which moisture inside the jacket can pass out and stop water droplets and wind from penetrating in. The zipper is made of corrosion-resistant nylon, and the nickel-plated zipper pulls last seven times longer than ordinary zipper pulls. Before this process, workers mainly used the inside out process. Now they have to turn the cold-weather garment over to do the final processing. These large snap fasteners are strong and sturdy, and they are located between the fiber material, so they will not damage the fabric even after repeated use. Its secret is that hidden layer of warmth. It keeps the air inside the human body surface and then heats it up to produce a kind of warm cushion against the cold of winter.