A soft shell jacket is a type of jacket that is made from a soft, stretchy material that is designed to provide both warmth and protection from the elements. Soft shell jackets are typically made from a combination of polyester and spandex, which makes them lightweight, breathable, and water-resistant. They are designed to be worn during activities such as hiking, climbing, or skiing, and are often used as a mid-layer or outer layer in a layering system.