Medium arch signature Superfeet shape adds stability and comfort to your running shoes, reducing stress on feet, ankles, knees, and back. Improves efficiency, reduces fatigue, and supports every step. Responsive EVOLyte carbon fiber cap and two layers of Aerospring Rebound foam combine to deliver exceptional comfort and smooth and efficient energy transfer through your gait from foot strike to toe off. Made to replace the removable liner in roomy to moderate-fitting running and walking shoes.