Built with 12 springs that cushion and support the foot, these insoles return some of the energy to the body for a "push off" with every stride. Many foot and ankle ailments stem from the impact of the body's weight while walking, which is why the five coils are positioned directly underneath the heel. Seven smaller springs under the ball of the foot further disperse the impact and cradle the foot. The suspension coils are only 1/4" thick, making them just as suitable for athletic shoes as for work boots, and undetectable until a step is taken. The insole also features honeycomb padding with valves that draw in and expel air during walking for constant circulation to keep the shoe dry and skin healthy. Men's sizes S (4-6), M (7-8), L (9-10) or XL ( 11-13); Women's sizes S (5 1/2-7 1/2), M (8-9 1/2), L (10-11 1/2) or XL ( 12-13 1/2)