With a revolutionary combination of merino wool in the arms and back and synthetic insulation in the chest and sides and you will be one happy hunter, not to mention warm and dry. Revolutionary Merino And Synthetic Midlayer, Midweight 260g Merino Arms And Back For Wicking And Temperature Regulation, Synthetic Insulation In Core Areas For Extra Warmth, and Silvadur Antimicrobial Technology For Odor Management.