The "ACROFOAM" has improved rebound resilience and "SORBOTHANE" hybrid cushioning for top athletes. Running assists with light propulsion. Assists in late half of road racing. Compatible sizes: 2S 8.7 - 9.1 inches (22.0 - 23.0 cm), S 9.3 - 9.6 inches (23.5 - 24.5 cm), M 9.8 - 10.2 inches (25.0 - 26.0 cm), L 10.4 - 11.4 inches (2 - 2 cm). If your shoes have insoles, please remove them and use them again.