The La Sportiva Tracer T-Shirt is cut with flatlock seams that stay comfortable against the skin even under the weight and friction of a running vest. S. Café fabric keeps things breathable and manages odor on long efforts, so pace and rising temps don't turn into a sticky, chafed mess by the final mile. Recycled polyester makes up the entire shirt, so performance doesn't come at the cost of using new material. What Our Gearhead® Experts Are Saying:"I ran a hot, three-hour mountain loop with a loaded vest and never once had to adjust for chafing or worry about how I smelled at the aid station. That's the difference between a shirt built for a track workout and one built for actual mountain running."