Features of the Pearl Izumi Men's Merino Long Sleeve Base Layer 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 Fabric Details Merino Wool/Recycled Polyester