Upgraded and reworked, On Running's Cloudswift 4 AD has an improved cage construction for better lockdown and a new water-repellent finish. The engineered mesh upper ensures airflow, while the sock-like fit offers a soft step-in. Below, a dual-density midsole features Helion superfoam on the top layer and a denser layer on the bottom for a more propulsive takeoff. Textile & Synthetic Upper/Synthetic Sole.