No size tag but it fits like a medium (20.5” pit to pit) Why we made this Our schedule isn't weather dependent there's always room to lace up and leave the day behind. For cold night and early morning runs, we made this lightweight pullover out of warm, cozy fabric and added reflective details to help us shine bright in low light. Key features lightweight Polartec® Power Stretch® Pro fabric helps you stay warm without weighing you down reflective details on the arms help you shine bright in low light comfortable elastic hem helps keep your top in place when you're hitting your stride imported Fit + function designed for: run fabric(s): Polartec® Power Stretch® Pro fit: loose length: hip