FLYTEFOAM® Propel technology in the midsole offers excellent bounce and toe-off. This lightweight foam formulation has a special high-energy return elastomer helping to put a spring in your step. Gain even more bounce with our SpEVA insole, which also helps the shoe last. To ensure a great fit, there's an external heel counter which holds your heel firmly, keeping you comfortable as you pound the miles. And we've added an AHARPLUS™ heel plug on the outsole to help you be able to run as long as you want. This ASICS High Abrasion Resistance Rubber is a tough rubber compound used to reduce excessive wear. All of this lets the shoe take the strain so you can concentrate on what matters: your breathing and pace.