ISPA is Nike’s experimental, boundary-pushing division. There’s a focus on functionality and each design is influenced by four defining principles: improvise, scavenge, protect and adapt. The latest sneaker to make an appearance is the Overreact Sandal, and it’s exactly as you’d expect. The React Foam tooling is borrowed from the Overreact and takes inspiration from improvised traction systems. And the uppers take a function-first approach, too. They’re layered up to ensure support and protection but have strategic openings throughout to promote air flow and keep your feet cool on the warmest days.