Description You can't go wrong with Wirecutter's top pick for the best thermal underwear. Our Aspect Base Layer Long Sleeve Shirt is a "city-to-trail shirt" and Wirecutter's "most versatile pick." They capture what we really love about this base layer top—it's endlessly versatile and the perfect companion no matter where the day takes you. It's soft and cozy against your skin and it keeps you warm, dry and comfortable. Plus it features industry-leading durability thanks to our (m)Force Technology. It has a slightly longer cut so it stays tucked in when skiing or snowboarding, and it has discreet thumb holes. Pair it with our Aspect High Rise Bottoms. "It's a versatile layer that handled the transition well from walking around in 30-degree-Fahrenheit temperatures to a hot and crowded house party.” - WIRED Magazine Product Features Natural and sustainable Merino Wool 180g reinforced with our (m)Force Technology for increased durability, dry times and recovery Versatile mid-weight base layer that is warm but not too warm Flatlock seams Backpack-friendly raglan construction Discreet thumb loops that keep your sleeves in place and disappear when you don't want them Printed neck label Removable care label Long cut that works great for layering and stays tucked in Fabric Details 84% Merino wool, 16% nylon 180 GSM fabric weight Soft 18.5M Merino wool (m)Force™ technology Care: Machine wash on warm or cold, hang dry, do not bleach or dry clean, iron on low wool setting. Learn more. Sizing/Fit Amber (in Black) is 5'7" wearing a Small; Mary (in Rum Raisin/Terra Cotta and Winter Blue) is 5'10" wearing a Small. Fits as a base layer close to your body Extra length for more coverage Sleeve Length (measured from collar to end of the sleeve) XS - 28" S - 29" M - 30" L - 31" XL - 32" XXL - 32.5" XXXL - 33" Not sure what size to order? See our size guide. Product Video