Reebok NANO X4 The Reebok NANO X4 men's fitness shoe represents the pinnacle of lightweight and breathable design within the Nano series. These Reebok training shoes are made with increased stability and support without unnecessary structural elements that add weight. The updated Flexweave® woven upper is ultra-light and a new ventilation panel in the middle of the foot allows for more airflow. Maximum stability is provided by the innovative Lift and Run Chassis system, while Floatride Energy Foam cushions every step. Reebok NANO X4