Nike Women's Flex Experience RN 4 Running Shoe synthetic-and-mesh Single-layer mesh and no-sew overlays keep the shoe supportive and light. Resilient foam midsole is durable enough to double as an outsole. Outsole hexagonal flex grooves promote maximum natural motion. Waffle outsole pistons help absorb impact and add responsiveness. Heel-to-toe offset is 7.2mm.