Reebok Nano X4 Mens The Nano X4 Training Shoes are one of the lightest and most breathable Nano iterations yet. These Reebok training shoes are crafted with enhanced stability and support, without excess design features that add weight. The updated Flexweave woven textile upper is ultralight and a new midfoot ventilation panel allows greater air flow. Ultimate stability comes from the innovative Lift and Run Chassis system, while Floatride Energy Foam cushions every stride.