Layer one matters most. But will any flatter and fit like our new thermal top? Lightweight grid fleece performs as a breathable base or solo layer. Flatlock seams reduce chafing for long-lasting comfort. We love it for: cold weather running 67% recycled polyester, 27% polyester & 6% spandex Lightweight grid fleece Warm, stretchy & quick-drying Tailored fit Flatlock seams Locker loop Elbow patches Machine wash cold, tumble dry low, don't bleach, mmkay? Designed in California, made abroad