Outside: 70% Micro-Polyester, 30% Merino WoolInside: 100% Micro-PolyesterClimaSense Thermoregulation Technology keeps you comfortable in all conditionsEngineered to adjust to your body temperatureInhibits the growth of bacteria that causes odorFast wicking and dryingUltra-soft brushed surface traps air and allows for increased airflow / breathability4-way stretch for ease of movementMidweight warmth (2.0) makes Cloud Nine extremely versatileUPF rating 25+Functional thumbholes and all flat seam constructionVendor Style Number: W8361 Terramar Men's 2-Layer Thermal Bottom