Tracksmith's best-selling Brighton Base Layer features an engineered Merino mesh, a stunningly soft, moisture-wicking blend that regulates temperature and is virtually impervious to odor. We designed the top as a training base layer to be worn under a mid-layer or jacket, but its seamless construction gives it a flattering fit that’s not too tight to wear all by itself. It’s built for a level of comfort to rival your favorite pajamas, and a level of performance without any rival at all.