The key to staying comfortable on cold days is staying dry. By putting polyester next to the rider's skin, it transports moisture away to the Merino layer where it can evaporate even as the wool acts as insulation. The base layer uses a set-in sleeve design for a versatile form-following fit to make layering easy. Features: 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 XS Polyester technical fibers are made from recycled plastic water bottles. Set in sleeve construction for easy layering and versatility.