Gore Running Wear Essential Base Layer WS Singlet 100% Polyester, Windstoppermembrane, Stretch: 88% Polypropylene, 8% Elastane, 4% Nylon Imported This singlet is ideal for windy, cooler days Elastic WINDSTOPPER insert on front, over shoulders and on kidney area Thin and soft fabric Minimized seams for less chafing The combination of materials ensures rapid moisture wicking and protects against wind chill