Worn 3 times!!! In EUC from smoke free/ pet free home!! Meet the Nano X3 training shoes with the all new Lift and Run Chassis system. A dome-shaped heel piece compresses under load when lifting to create a stable platform, then softens when you push off to run. It all rides on award-winning Floatride Energy Foam that gives you lightweight cushioning to make that run the easiest part of the workout.