Excerpt from Owner's Guide: Purchase W2 Sport Basic T-Shirt. Recycle packaging. Wear all day. Sleep in W2 Sport Basic T. Run 5k. Grab mountain bike. Clean ''impossible'' single track line. Afternoon sport climb. Sleep in W2 Sport Basic T. Early morning run. Pick up soccer followed immediately by bakery breakfast. Camping weekend. Monday morning paddleboard. Wash. Repeat. A nylon core is wrapped with wool to create a hardy fiber without bulk or weight. Weightless Wool is designed to be softer, more durable and lighter than synthetic workout fabrics. A perfect fabric when used alone for warmer days of aerobic work or layered to add warmth in colder activity. 145g/m2. 87% Merino, 13% Nylon.