FEATURES OF THE SMARTWOOL MEN'S MERINO SPORT 150 LS 1/4 ZIP TOP Size small Flatlock seam construction designed to minimize chafing Offset shoulder and side seams designed to increase comfort Underarm and back mesh panels to help keep you dry where you need it most Reflective elements for added visibility in low-light conditions Fabric Details 56% Merino Wool, 44% Recycled Polyester Back, Underarms: 56% Merino Wool, 44% Recycled Polyester