The Arc’teryx Rho Merino Wool Crew Neck Top delivers natural performance across multiple activities with its innovative 240gsm 18.5 Merino construction that wraps around a durable nylon core for exceptional longevity. Featuring body-mapped articulation that follows your movements during technical pursuits, this versatile base layer naturally regulates temperature and fights odor during multi-day adventures from alpine climbs to backcountry tours.