Without a good base layer, the rest of your outfit isn&';t able to function as designed. As the first barrier between your skin and the elements; it&';s critical a good baselayer be warm, comfortable, and moisture-wicking. The Pyrex Extreme Pant has all those things in a durable, well-cut package. The proprietary GRIDtech 4-way stretch fabric works as a second skin, providing additional warmth without weight and maximum breathability. Polyester/Spandex Blend Grid Fleece For Added Warmth 4-Way Stretch Polyester, Highly Breathable & Moisture Wicking Fabric Flat-Lock Seams Mid/Late-Season Base Layer