"Men's On® Core Long-T: The On® Core Long-T is a lightweight men's long sleeve running shirt built for cool-weather training, daily miles, and easy layering. When temperatures drop but a full jacket feels like too much, this is the kind of top you reach for - soft enough to wear comfortably against the skin and breathable enough to keep up when the effort picks up.The fabric is a 92% polyester/8% elastane blend that moves with you and helps pull moisture away from the skin as you run. The streamlined fit keeps things out of the way during arm swing and stride, so there's nothing distracting you from the run itself. It also works well as a base layer under a vest or running jacket when conditions call for an extra layer of warmth.Why Our Fit Experts Love It""I grabbed the Core Long-T for a cool morning run and it was exactly what I needed - light enough that I didn't overheat once I got moving, but warm enough at the start that I wasn't wishing I'd brought a jacket. The fit stays clean and doesn't bunch up, which I really noticed on the longer stretches."" - Sean, Road Runner Sports Fit Expert, Chula Vista, CAWho It's Best ForThe Core Long-T is a strong choice for male runners who want a reliable long sleeve for cool-weather runs without the bulk of a jacket. If you log a lot of early morning or fall miles and want something that manages moisture, moves freely, and layers easily when needed, this top fits that role well. It works across a range of efforts - from easy recovery runs to steady-state workouts - making it a practical everyday training piece. VIP Family members can take the Core Long-T for a 90-Day test drive with our Perfect Fit Guarantee."