NIKE Women's Flex Experience Run 4 Premium Running Shoes (9 B(M) US, Green/White) Single-layer mesh and no-sew overlays give lightweight support. Resilient foam midsole is durable enough to double as an outsole. Waffle outsole pistons help cushion impact and add responsiveness. Outsole hexagonal flex grooves promote maximum natural motion. Heel-to-toe offset is 7.2mm.