Brooks Atmosphere Singlet Men's (2020) Stay cool when the intensity rises in the Brooks Atmosphere Singlet. This lightweight running layer uses a breathable, sweat-wicking fabric to help you stay dry during your runs. Breathable, lightweight fabric wicks away sweat to keep you cool. Bonded seams and minimal finishing details in the arms and neckline provide a minimal feel. Antimicrobial finish prevents odors in between washes. Hanger loop Sizing Small: 35-37" chest Medium: 37-39" chest Large: 40-42" chest X-Large: 43-45" chest *Measurements refer to body size, not garment size.