lightweight and flexible. the nike flex experience leather boys' running shoe is designed with reduced layering for a lightweight fit and flex grooves at the outsole for natural range of motion. a midfoot panel and side perforations create superb lockdown and ventilation in this ultra-comfortable shoe.. benefits. leather upper with synthetic overlays for comfort and support. side perforations for a breathable fit and minimal bulk. phylon midsole for lightweight cushioning. waffle pistons for added cushioning and response. rubber pods at heel and toe for extra durability in impact zones. flex grooves for enhanced flexibility and a smooth, efficient stride.