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 : ClimateTEK™ dynamically responds to your body temperature to keep you cool when things heat upGreater Arm Mobility™ helps extend arm and shoulder range-of-motion so you can move freelyMoisture Movement Technology™ helps wick moisture away from the skin to keep you dry and comfortableSilver-based FreshTEK+™ odor control helps keep you feeling fresh through long hours of wearStain-repellent finish helps keep fabric looking clean and easy to maintain through repeated wearVentTEK™ mesh panels provide ventilation in key areas to help keep you cool and comfortableWrinkle-resistant finish helps fabrics stay smooth through daily wear, reducing the need for ironing, Convenient locker loop, Breathable mesh insets at sides, back and under arms, This product contains materials that meet the bluesign® sustainability standards Women's VentTEK Underscrub Baselayer in Black, Size: XS by Ariat