NIKE Men's Hyperwarm Base Layer 88% Polyester, 12% Spandex Imported DRI-FIT SINGLE KNIT FRENCH TERRY PROVIDES WARMTH AND MOISTURE MANAGEMENT FOR ULTIMATE COMFORT AND MINIMAL DISTRACTION MOCK NECK FOR COMFORT AND COVERAGE FLAT-SEAM CONSTRUCTION MINIMIZES IRRITATION AND CHAFING SIDE PANELS AND UPPER BACK BODY FEATURE DRI-FIT MESH FABRIC FOR BREATHABILITY. TWILL HEAT TRANSFER SWOOSH ON MOCK NECK; TIGHT FIT AND WARM MATERIAL HELP RETAIN BODY HEAT AND KEEP OUT THE COLD.