This is our heaviest base layer, at 250g/m2. It combines our 18.5-micron responsibly sourced Merino and recycled polyester technical fibers in a remarkable construction that positions the polyester next to your skin for maximum wicking while the wool faces out for superior insulation. With its long sleeves it is the ideal garment to layer beneath one of our AmFIB(R) jackets. Thumb loops keep the sleeves in place as you pull on your jersey. Features: Mid-weight Transfer Merino fabric combines wool and recycled polyester for sustainable technical performance. Unique plated fabric construction places polyester next to skin and merino on the exterior for superior moisture transfer and thermal regulation. Made using fine 18.5-micron merino wool for superior comfort. Recycled Repreve(R) XS Polyester technical fibers are made from recycled plastic water bottles. Set in sleeve construction for easy layering and versatility.