NIKE Free Balanza Womens Training Shoes 599268-003 Synthetic Breathable mesh Nanoply upper blends breathable mesh with stretchy synthetic material for a second Phylite midsole doubles as an outsole for lightweight cushioning, durability and reduced weight Deep outsole flex grooves for natural range of motion and flexibility Laser cutouts map the foot in a circular pattern for flexibility and ventilation Rubber pods on the heel and forefoot for multidirectional traction on a variety of surfaces