EVA (Ethylene-Vinyl Acetate) an elastic co-polymer very similar to rubber and also used in household and industrial applications. EVA is considered environmentalyly friendly in that it doesn’t use chlorine in its production, and can be recycled into products such as playgrounds or industrial mats.EVA provides cushion, spring (rebound), and is resistant to hardening and cracking. It also resists UV radiation, doesn’t absorb water, and stays flexible in the cold, all of which make it very useful for outdoor footwear. Soft and flexible, EVA is technically a foam instead of a rubber, as it is formed by expanding plastic and trapping pockets of gas (air) in various densities. An EVA midsole not only provides rebound and cushion, but it protects the feet from impact as each foot strikes the ground. The rebound in EVA helps you spring off of each stride.