Dual Fusion Run ST Women's Running Shoe. The Nike Dual Fusion Run is a lightweight, highly flexible running shoe that gives superior cushioning. The minimal upper delivers support only where it's needed and the dynamic lockdown lacing system offers superior fit. Features a dual-density midsole system consisting of a firmer Phylon carrier and a softer Phylon internal footbed to offer the perfect blend of maximum cushioning. A classic waffle outsole delivers a smooth heel to toe transition without adding unnecessary weight.