This Classic Thermal Base Layer ¼ Zip is one of Smartwool?s heaviest base layers with an updated slim fit and is made of 100% responsibly sourced Merino wool. The interlocking knit provides comfort, breathability and thermoregulation, so you can stay comfortable when embarking on your latest adventures. With a flatlock seam construction and offset shoulder and side seam, the garment reduces the effects of chafing and a 25cm centre-front zipper has a semi-locking slider so it stays in place. Smartwool Men's Classic Thermal Base Layer 1/4 Zip - Black | George Fisher