We gave the base layer an upgrade with performance fabric and a slimmer fit. Our VentTEK™ Underscrub features built-in breathability for extra warmth without overheating. VentTEK Underscrub Baselayer Product Features : Silver-based FreshTEK+™ sustainable odor resistanceVentTEK™ technology puts airflow where you need it most to keep you coolClimateTEK™ dynamically responds to your body temperature to keep you cool when things heat upStain repellentMoisture Movement Technology™ helps keep you dryGreater Arm Mobility™ lets you move freely, Convenient locker loop, Breathable mesh insets at sides, back and under arms, This product contains materials that meet the bluesign® sustainability standards Men's VentTEK Underscrub Baselayer in Black, Size: Medium by Ariat