The Nike Flex RN 2019 brings stretch to your run. A stretchable knit upper wraps you in softness as it expands and contracts along with your foot. Dual-density foam layers supply durable cushioned comfort, while hot-knife grooves on the outsole give you flexibility heel-to-toe. Four-way stretch knit upper expands and contracts with your foot. Dual-density Solarsoft foam cushions every step. Textured for traction heel-to-toe with hot-knife siping. Synthetic overlays around the laces provide structure for a secure fit. Heel and tongue loops stretch the opening so your foot easily slides in. Flex grooves on outsole move and bend for ultimate flexibility.Upper - Textile, Lining and Sock - Textile, Sole - Other Materials.