NIKE Women's Flex Experience RN 4 Running Shoe synthetic-and-mesh Hexagonal flex grooves let your foot move more naturally Single-layer mesh and no-sew overlays keep the shoe supportive and light 7.2mm heel-to-toe drop enables a more natural motion Injected unitsole midsole doubles as the outsole for cushioning and durability Waffle outsole pistons absorb impact and spring back for added responsiveness