Excellent comfort designed to cross the finish line. Durable synthetic leather/mesh upper. Breathable fabric lining. ComforDry Sockliner for a cooler, drier, healthier environment. Flexible, traction-patterned rubber sole. Twist GEL Cushioning System attenuates shock. AHAR Heel Plug enhances durability in key areas. DuraSponge enhances cushioning and durability. Impact Guidance System (I.G.S. ) enhances the foot's natural gait. PHF (Personalized Heel Fit) for a superb fit. 3M Reflectivity enhances visibility during low light hours. Solyte midsole improves cushioning and durability. Space Trusstic System allows for more efficient foot function. APMA (Seal of Acceptance)