These soft and stretchy unders are made from capilene, an insulating fabric spun from 100 percent recycled polyester. The synthetic threads perform about on par with wool. Capilene is also just about as comfortable, all while being light and quick-drying. Patagonia sells the base layers in two thicknesses: midweight and a heavier thermal weight. They come in men’s and women’s sizes, and the tops are available in a crewneck or collared zip-neck. I tested these in the fall in Minnesota and in San Francisco, so I wore the midweight version with a crewneck top.

Taking advantage of the precision afforded by working with synthetic fabric, Patagonia has made some interesting design choices. The garments are smooth on the outside, and have a subtly embossed diamond grid pattern on the inside. The company says this diamond pattern creates little pockets that trap heat and help wick moisture. That claim is next to impossible to verify, other than to say: The fabric did keep me about as warm as merino wool.

Like most Patagonia apparel, these fit a little looser than the same size would from other brands. Even though I tend to like my base layers snug against my skin for maximum warmth, here I appreciated the extra room in the shoulders, in the groin, and under my arms. I wore them for two days straight on a canoe camping trip—even sleeping in them—and after a wash a week later, another two days commuting to and from my office. They didn’t chafe or bag out, and the elastic points never pinched. After each multiday wear, they did stink a little—more than wool would in the same scenario, but miles better than other synthetics I’ve tried. If you’re avoiding wool because of allergies or because you’re eschewing animal byproducts, this fair-trade certified two-piece is a solid alternative. —Michael Calore