For unbeatable defense against cold weather, SmartWool's NTS Mid 250 Zip T delivers with the softness, warmth, and moisture-managing performance of pure merino wool. NTS (next to skin) Mid 250 base layer for cold-weather performance. Fine merino wool fibers provide supersoft, itch-free comfort and warmth SmartWool breathes, manages moisture, regulates temperature, and naturally resists odor. Interlock knit; UPF 50+ for maximum protection from the sun. 8 in. (20 cm) center-front zipper with semi-locking logo slider. Back body seam wraps to front for body-enhancing fit. Raglan sleeves eliminate top shoulder seams for comfort when wearing a pack. Flatlock seam construction designed for chafe-free comfort. Heat transfer logo at left sleeve cuff. Form fit: Slim fit; follows the contours of the body.