Soft and breathable, the ultrafine merino wool of the naturally odor-resistant men's REI Co-op Merino 185 long-sleeve half-zip base layer top is ideal for sweating on the trail—and sleeping in a tent. - Ultrafine 185 g merino wool offers a soft feel without any itchiness - Made with 100% merino wool that naturally breathes, wicks away sweat, dries quickly and resists odors, making it an ideal multiday trip companion - UPF 30 sun protection - Half-zip front helps with venting; standing collar and chin guard for protection - Flat seams and merrow stitch construction eliminate chafing - Underarm gussets allow full range of movement - Designed to hug the body for optimum performance - Field-tested on its own and as a base layer while hiking, running, rock climbing, cycling, skiing and camping in diverse climates across the U.S. New condition Size Medium Approximate Flat Lay Measurements 21.5" across chest 28" shoulder to hem