Women's Paradox Performance Merino Blend Zip-Up Long Sleeve Base Layer zipper cover to hold 1/4" zipper in place and also thumb holes for simple layering and insulation Structured material made with 84% Polyester, 11% Merino Wool and 5% Spandex Patented Dri-Release and Anit- Odor wicking material for high intensity workouts Stretch, lightweight top provides comfortable warmth without the itchiness Dries 4x faster than Cotton, perfect for all outdoor activities in the winter cold!