The Smartwool Men's NTS Mid 250 Zip T is made of merino fabric designed to keep you warm, dry and odor free no Matter how active of a lifestyle you have. The Interlocked knit of this Zip T provides a seam-less construction for less unwanted abrasion during movements. Best used as a first layer in colder outdoor activities, with the option to povide ventilation as your movements intesify and your body becomes more heated. Features of the Smartwool Men's NTS Mid 250 Zip T Interlock knit 10in. (25 cm) center front zipper with semi-locking logo slider Shoulder panels eliminate top shoulder seams Flatlock seam construction designed to eliminate chafing