When summer rolls around, we still rely on the power of Smartwool's merino wool for odor-fighting, temperature-regulating tech. The Classic All-Season Merino 1/4-Zip Baselayer Top is lightweight enough for high-temperature adventures, offering protection against blistering heat, trailside foliage, and our own sweat production. Merino wool's natural attributes translate into comfort on fall backpacking trips and spring backcountry tours, too, and the nylon-core construction places the techy wool next to skin for ultimate softness and reliable performance. Finish this style off with a slim fit and articulated seams for movement-mirroring mobility and an easy-to-layer silhouette, and we're sure to select this first layer no matter the season.