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 a thin layer of Aerospring™ Rebound comfort foam for a versatile fit combine to create smooth and efficient energy transfer throughout your gait, from foot strike to toe-off. Made to replace the removable liner in moderate to tight-fitting running and walking shoes.