Stay cool as your training heats up. This women’s Reebok running t-shirt uses breathable ACTIVCHILL. Reebok’s Coolest. Fabric. Ever. Join over six million others in experiencing the instant cooling sensation of our top-performing ACTIVCHILL technology. Placed where you need it to help keep you cool. Mesh on the back raises the comfort level even more, and reflective details add visibility in low-light conditions.