4 oz/yd2 / 140 gsm, 100% recycled polyester Coolcore® mesh; Recycled material made from plastic bottles; Coolcore® technology is chemical-free, mechanically engineered performance that doesn't wash out; Moisture wicking, thermal regulating, UV 15-39 protection with no topical treatments; Self-fabric collar with integrated collar stand and built-in collar stays; Sustainable fabric manufacturing practices. Learn more at Coolcore.com