These jackets are proven as mid-layer or outer layer jackets of Micro-fleece.
Fleece is a soft, lightweight, warm and comfortable fabric. It is hydrophobic, holding less than 1% of its weight in water, it retains much of its insulating powers even when wet, and it is highly breathable. These qualities make it useful for making clothing intended to be used during strenuous physical activity; perspiration is able to readily pass through the fabric. It is machine washable and dries quickly. It is a good alternative to wool (of particular importance to those who are allergic or sensitive to wool).
Polar fleece (also known as microfleece), usually referred to simply as "fleece," is a soft napped insulating synthetic fabric made from Polyethylene terephthalate (PET) or other synthetic fibres. A light and strong pile fabric meant to mimic and in some ways surpass wool. Fleece has some of wool's finest qualities but weighs a fraction of the lightest available woolens.