Filson's Jac-Shirt has been a staple of their fall lineup for years. This version adds a dry finish Cover Cloth exterior and interior to help block out the wind while staying breathable. The tightly woven cotton fabric sandwiches a layer of lightweight polyester insulation that continues to hold in heat even if it gets wet. Two patch button-flap chest pockets and two flannel-lined hand warmer pockets offer storage, while polyester twill lining on the sleeves helps it slide easily over inner layers.