Tuli's® Heavy Duty GEL Heel Cups, provide additional thickness and support for athletic performance. They perform better in athletic shoes or more spacious lace-up shoes. The multi-cell, multi-layer design absorbs shock and returns impact energy just like the system naturally found in your feet. Upon impact, they bear down and rotate with the normal motion of the foot to absorb the shock of walking and running; keeping your feet, knees, hips and back in alignment for maximum comfort and performance.