From the product description: Designed for performance layering in transitional weather utilizing the benefits of wool as an optimal natural insulator. Enabling thermal conductivity between the skin’s surface and the interior garment fibers. Thermoregulatory material attributes complimented by silhouette design to allow for ease of insulation+/ventilation. Polartec® Power Wool™ High stretch, unique bi-component knit: next to skin fine merino and synthetic external fibers. Harnessing the natural powers of wool, also naturally antimicrobial material benefits. Synthetic blend allows for better surface durability, optimal shape retention and faster dry time. 10”exposed front zipper with high security collar design. Straight cut body for natural fit to torso with added sleeve length for thermal comfort. Reduced noise design patterning, seaming + strategic elasticated hem finishing. 54% Nylon, 26% Spandex, 21% Wool