Smartwool Merino 150 Base Layer Short Sleeve - Women'sFEATURES Our lightest weight Merino jersey fabric uses a nylon core to increase durability while still keeping 100% Merino wool next to skin Raglan sleeve design eliminates need for shoulder seams Side seams wrap onto front for enhanced fit Stretch merrow stitching designed to elevate comfort, range of motion, and fit Select colorways feature plant based dye technique UPF 20+