Fleece Is made of synthetic materials, generally polyester, to give stretchy and soft insulation that will keep you warm when wet. Fleece works best as a second layer. It is known for its durability. Fleece offers a wide range of options varying from air-permeable to windproof. As a part of a mountaineering layering system, fleece is often a light insulation layer, and the degree of warmth and protection can be chosen based on other layers in your system or how much warmth is required.\r\nWool used for outdoor clothing is Merino, the finest, most flexible, and softest wool fiber available. Wool is a renewable, natural fiber that breathes most similarly to your skin, keeping you comfortable. Wool comes in several different weights ranging from a microweight up to a heavier sweater weight. There are even nylon-faced jackets insulated with wool that make perfect insulation layers. Wool transfers moisture away from your body in a vapor state, therefore allowing it to breathe efficiently. Due to this moisture management, it also doesn’t retain odor. Far less stink!