Looking for a base layer that will keep you comfortable in any situation? Look no further than the Smartwool Classic Thermal Merino Base Layer. As one of the heaviest base layer tops in the Smartwool collection, it is made with 100% responsibly sourced merino wool and designed to provide enhanced comfort, breathability, thermoregulation, and odor resistance. The slim fit is updated to improve functionality while enhancing aesthetics for a range of body shapes, and the back body seam wraps to front for a body-enhancing fit. The crew neck with raglan sleeves provides a comfortable fit, and the flatlock seam construction is designed to minimize chafing. The 8" center front zip with semi-locking slider makes it easy to put on and take off, making it the perfect option for throwing over other layers when extra warmth is required.