ASICS Women's GEL-DS Trainer 16 Running Shoe 100% Synthetic and mesh Rubber sole Heel measures approximately 1.5 inches" Impact Guidance System (I.G.S.) ASICS design philosophy that employs linked componentry to enhance the foot's natural gait from heel strike to toe-off. Clutch Collar System A descendant of the Heel Clutching System, an Endoskelatal collar compliments the exoskelatal heel counter for a uniquely secure fit. Guidance Line