Salming Miles Women's Running Shoe - SS16 Synthetic Synthetic sole 2 Layer upper construction - Creates a lightweight, durable design with plenty of breathability. Exo Skeleton design - Helps stabilize the foot while relieving pressure on the MTP joints. Heel cup design - Provides a adaptive heel fit in a lightweight package. Recoil midsole technology - Absorbs negative impact forces and releases a higher rebound energy effect in the toe off phase. Torsion Efficiency Unit - Is a transparent TPU unit that creates a absorbs negative impact forces and releases a higher rebound energy effect in the toe off phase.